Well, you would need to have a logic analyzer like an inexpensive saleae clone and a program like Pulseview to capture and decode the bus signals but you sorta need to have some experience doing it. I can post a setup file for Pulse view (or Saleae if you use that) to simplify the process if you think this is something you want to try.
It might just be easier and more effective in the long run to just upgrade your alarm main board to a vista-20p or something. They are fairly inexpensive.