FWIW
I fly Dynon's Skyveiw with an IFly for a back up. Dynon will soon ship thier ADSB receiver so I looked into how GPS sources are used by ADSB. It turns out that the Extended Squitter message from your ADSB (out) transponder contains a position source quality value. This tells all listening just how good the position fix you are reporting is. When using the non-TSO'd Dynon puck (integrated receiver/antenna) the transponder reports the fix quality as unknown. I suspect this means that ATC will not/can not use it for primary seperation.
I looked into this with an eye towards 2020 ADSB compliance. Hopefully someone out there is working on an inexpensive TSO'd puck to act as a certified position source for the ADSB out transponders.