Design Diagram:

IP Phones are currently registered across the internet to Cisco PhoneProxy -There is IPSec Site-to-Site VPN in place for Data Traffic "only"

Question:

I want to setup SRST on the local router incase connectivity is lost btwn the ip phone(s) and the phoneproxy and/or the phoneproxy and call manager.

How will the ip phone(s) treat SRST if any of the above scenarios are introduced?

Since the PhoneProxy rewrite the XML files on the phone - Is it possible to have SRST in this design scenario?