I stumbled across this thread while looking for more info on EADS/Cassidan P25 systems. I've spent a little bit of time running Pro96Com on this confirmed EADS/Cassidan P25 system: Golden Gate Bridge Highway and Transportation District (700 MHz ACIS) Trunking System, San Rafael, California - Scanner Frequencies
The above system definitely has normal P25 radio IDs. Since it is still in early stages of development, there was very little voice traffic and I mostly watched talkgroup affiliations and did traffic analysis.
Radio ID "0" is commonly reserved for outside systems being patched in. On the EBRCS
system, the 0 ID was used extensively on talkgroups where users had a mix of old and new radios. Clearly there must have been dozens of console patches to route all the analog audio from multiple conventional frequencies into the system, but every patch showed up as radio ID 0.
Is it possible that RCMP "O" division is still using their conventional 420 MHz frequencies and being patched in? From looking in the database, it looks like both the RCMP conventional and P25 systems are encrypted, so the obvious analog-sounding audio wouldn't be apparent. But based on your description of many 0 radio IDs, mixed with a few normal looking ones, it sounds very likely that you're looking at a system still transitioning in its users from their previous system.