Thanks!
I think, this is not standard "USB" thing, there is no need for synchronous transfers and so on. All is needed is to send proper sequence of bytes.
So I've ordered that IP2721, and when it will arrive, will just try to "record" it's output byte sequence with analyzer and just replicate it with PIC.
Existing, software based PD/QC triggers are based on STM8 chips, so I guess, PICs should also be capable.