Just confirmed this with an XTS2500 on the new system (receive only). They are on the new system, encrypted (maybe just for now or maybe forever). The audio is being decrypted and patched to the EDACS. I can hear P25 feedback audio on the EDACS which confirms they are on the new system and that it is patched to the EDACS. I am on TG 11003, I can see all radio IDs and get the double LED flash for an encrypted transmission. I get no audio unless I use a scanner on the specific frequency.
Also, the radio ID that shows up on my Harris P7100ip is the same for every transmission. So, it's patched through to just one radio on the EDACS.
There are still a few units transmitting on the EDACS only like 1-3s cruiser radio. That's not going over the P25 system but the dispatcher is acknowledging on it which is then patched back to the EDACS so the officer can hear.