Like I tell my customers who think that BacNet is a do-all integration, the first time that you have to replace a module and download memory, or you need to change a program, you're screwed. These integrations take both parties, especially on startup. Later down the road there will be issues like you have here. Many times the older systems were not ready to be seen by other system, they had to be configured to do so which takes the original vendor.
Keep in mind that many Supervision systems were before BacNet was invented, if you're talking U551, hopefully you're using Supervision InterOp which was later than Supervision. As far as seeing zone temp, the microblock does not output BacNet, you have to hang a BV status in the program which will require a rewrite.
HotRod
Controls..some days your a hero, some days your a zero. Direct acting since 1992.