Hey Zac, I will weigh in here, I own several XTS5000 radios including Digital 800 trunking & a VHF one. I live in central North Carolina and use my VHF XTS5000 quite often and have no issues decoding MDC-1200 and Unit/radio ID's using the steps I have typed below...
In order to use MDC-1200 on your radio I would make sure your Flashcode has a minimum of the following anyways:
H35 - Conventional Systems Operation
Q806 - ASTRO Digital Operation
H14 - Enhanced Digital ID Display
Q182 - Radio Control Protocol
I program radios myself so naturally my flashcode has more, but those are just the minimum for MDC-1200. Next you have to read the radio, under Conventional click on the MDC tab, when it expands you have to click MDC System and under the General tab make sure you check mark Leading PTT-ID and Trailing PTT-ID, then under the Advanced tab I have check marked Emergency Alarm RX Indicator and for Sel Call/In-Call reset I made it Manual. Since I am assuming you just want to decode MDC and not actually send any out or transmit any, we are done with this part.
Go back out to the main menu for CPS and expand Conventional Personality. Once you make the personality you want to decode the MDC on click on the Signaling tab, make Signaling Type to MDC and make sure System Number underneath it is 1. Click the MDC tab now and make sure under Decode you have check marked: Selective Call Decode and Call Alert Decode, and for Unmute type make it: Or. Under that you can leave the Encode portion alone as long as you aren't going to transmit any MDC data.
I hope this helps, PM me if there's any more issues or just reply on here.
••David