If, in fact, you can ‘monitor’ the door/windows sensors with both the Alarm Panel and Vera I would suggest using Vera and PLEG as the logic portion of your H/A needs and let the alarm panel handle the security side. I’m fairly certain that you are correct in the understanding that Vera does NOT have an interface with that Alarm panel, so no way to set the Home/Away/Night modes via Vera. This was the primary reason I went down the path of creating my own ‘Security System’ using the Vera Secure - but driven by logic using PLEG and not the built in methods.
I’m also not sure what kind of control (logic) the 2 Gig alarm panel might offer, such as scenes or scripts, but I doubt it would rival the power of PLEG. Therefore your Vera Secure may be the better platform for controlling all the items you want to turn off or disable while away, plus you could also get additional notifications of these things actually occurring. If it were me, I think I would leave all the z-wave devices on Vera and not bother trying to bridge the panel at all.
I hope you find an answer and would love to see whether or not two controllers can monitor the sensors at the same time.