Custom importer and GetTimeInfo8

I'm working with h264 video muxed into an mpeg2 transport stream. I also have audio in an mpeg2ts that I am trying to sync up with it. When importing the videos directly into premiere pro CS6, they are both given a start time of 00:00:00:00 even though they should be different in order to sync.

So our solution, to avoid any sort of reencoding, was to append our own PES packet to the stream that would contain the time information we needed and then write a custom importer to look for and read this packet. This importer would defer to the built in MPEG importer (thus return imBadFile for imGetInfo8 and imOpenFile8 selector) and would listen for othe imGetTimeInfo8 selector at which point it would fill in the time information.

The problem I have is that the imGetTimeInfo8 selector is never sent! I tried this husing both the SDK_File_Importer and SDK_Custom_Importer samples as a base, on multiple test files. The videos still seem to load into Premiere just fine (still with the 00:00:00:00 time code though) so it's clearly going through the MPEG importer after I defer to it. I'm debugging in VS so I can see that I get the following selectors:

38 imGetPrefs8

38 imGetPrefs8

57 imQueryContentState

37 imGetInfo8

60 imQueryStreamLabel

(this repeats a total of 3 times)

I'm assuming that there's some series of flags/fields that I need to have filled out a certain way in order for imGetTimeInfo8 to be sent, but I can't figure them out and the documentation doesn't tell me enough (at least not as far as I can tell). Or maybe I'm failing to  I have left all the methods from the samples 'as is', except for returning the imBaseFile where required, and changing support from the .sdk(c) to the m2ts formats.

So in short, my question is: What needs to happen in order to ensure that GetTimeInfo8 gets called, namely when passing the majority of the import to an existing plugin?

Thanks