For those who don't know yet, the Irving Public Safety trunk has now rebanded. The frequencies that were above 865 Mhz are now all 15 Mhz lower. For a complete listing for all of the LCNs with the co-responding frequency you can find it here.
Also there is a new VHF P25 Test trunk that has been reported to be active in the Irving area on the DFWscan Yahoogroup. I haven't been able to hear it here in Plano yet so I am not sure if it is still active or not. Here is the message details from the DFWscan posting about this new test trunk.
There's a P25 trunking system being tested in the DFW area for the past couple
WACN = 1
SYSID = 7
Implicit Mode (no freq info)
156.7500 morse code id WD2XHY
WD2XHY is an experimental license to EF Johnson. Their location is in Irving,
near the airport. I think this solves some of the mystery systems people have
heard in the past with the WACN of 1 and SYSID of 7.
Here's an old link of one system I noticed back in April / May of this year: