strange happenings on AFP channels, ACT

[Longreach]

Hi, all, was in Canberra today, having a bit of a scan at lunchtime. did a normal band search round the 468mhz band and got the usual AFP encryption but noticed on Z2ch42 (468.875) and Z2ch55(469.200)(both with NAC 293) that when the encryption voice ended you would get short bursts of data. the funny thing is it would show up on the PSR500 as a trunked channel when the data came about. the data burts sounded like the start of a P25 Digital convo but would be continuous instead of going onto the usual digital white noise(on my IC208H) or encryption(on the 500).
the scanner screen(psr500) would alternate between the following when the data was about

the T would be on top corner
P25 469.20000
SY: --- R --- S ---

The T in top corner
P25 469.20000
99% N293 W-----

When the conversation would pick up again it would go back to standard tune screen

DG 469.20000 and flashing P293
you would also hear the encryption

I saved the trunk like screen in my scanner and it saved as a trunk system.

anyone got any ideas?

cheers all