Good luck on that, I'm pretty sure I've read every single Judgment related interview, and none of them specifically mention "canon" as far as I know. As I've said before in a previous discussion, really post proof or retract. There is enough "hearsay" going on, and people thinking they remember IGA saying something without actually posting any evidence that they aren't misrembering things, using misleading paraphrases or putting words into his IGA's mouth.
I know some people try to twist his quote from gamespy to mean the story doesn't mean anything;
GameSpy: People have been wondering how characters from different Castlevania time periods can appear in the same game. Is this explained in the story mode?
IGA: Yes, the story of why all these characters from different time periods come together is explained, but the story is not the main focus for Judgment. The main focus of this game is a celebration of the franchise's 22-year history, so I wanted to bring these characters together like a festival.
But that quote doesn't really discuss a concept of "canon" at all. He even says that things are explained. Yes he also says the main focus is gameplay, not the story. But he says that about many of the castlevania games in other interviews, such as the interview section I posted above previously.
There is a similar comment in an earalier (before the above interview) Nintendo power preview, but its yet another quote that doesn't say anything about canon, but people have interpreted to IGA meaning "canon". Still that's fan interpretations, not necessarily IGA interpretation.
Edit: Ok, I found my ecclessia nintendo power issue (July 2008) a few interesting comments from IGA in it.
At the time he wrote the article he said he considers the N64 games to be a "gaiden (subseries)" of the Castlevania franchise. This translation of him doesn't mention anything about canon, and uses yet another interpretation of "gaiden" than the usual "side story" translation some interviewers make. He goes onto praise the series as having a
"unique take on the Castlevania world".
Its a strong change to his stance on the games a decade ago when he pretty much completely rididculed them.
Later he goes onto mention CotM, he doesn't state anything about it being canon or not. He gives it praise as well, saying that while he didn't work on it,
"he feels connected to it some way".
He goes onto mention that he hired the director of CotM into his Castlevania team.
As for Legends, he's quite clear with his disgust of it (like in every interview he brings it up).
Aside from Legends all these games [adventure and Belmont's revenge] were made well before I joined Konami...Legends remains something of an embarrassment for the series. If only that development team had the guidedance of the original team on the series!
One of the more interesting comments is his discussion of Symphony of the Night. Its quite clear he loves it. We all love it. But something he said that came off interesting to me was his comment about Symphony starting out as...
"...something of a side story for the series, we were able to break alot of Castlevania conventions and introduce a lost of new elements that we still use today."
The issue doesn't go into any details on Judgment however, I'll check a later issue.
Alright here is the paragraph in the August 2008 issue of Nintendo power. It states (noting that article is discussing an incomplete version of the game before IGA had finalized all the details);
"As for how all these characters from thorughout hte ages wound up fighting each other, Iga remains quiet about the story details, but urges players not to worry about it. "When making this concept we wanted to develop a game that was very lively and had lots of things going on at once, almost like a festival," he states. "To create such a game we decided to ignore the time line of the [series], which is normally very difficult in most cases. However, the end result will allow players to see very interesting matches in the game, since many of the characters have been pulled from different Castlevania titles."
Knowing the fact that IGA has admitted that he comes up with gameplay before he decides on a story, this would seem to imply that in the early version that lacked any storyline, he hadn't thought up the time travel plot yet.
Later interviews such as the one I posted above, he discusses how the storyline they finally figured up, allowed the game to fit, and gave an explanation for how it could fit. This may be one of those cases where IGA changed his mind after the fact, in this case while still developing the game. Its really pretty difficult to take anything seriously that was quoted during alpha/beta version of the game over stuff later said when the game went gold, when his comments contradict each other.
A later nintendo power issue, the special holiday 2008 issue (that's December 2008/Januarary 2009 bonus I think) states in its review of the finalized release version;
"Longtime vampire hunters should especially appreciate the interactions between characters and the attention to continuity in Story Mode."
It was noticed by many reviewers, and even commented upon in a few interviews that contrary to IGA's previous statement he went out of his way to make the story plausible, and to give it an explanation. It wasn't just a storyless arcade game. For a game that IGA had originally believed ignored the timeline, he went out of his way to explain how it fits into the timeline with the final release.