Some success today.

The voicemail to email issue turned out to be an Exchange issue.

We are running exchange 2010. It did not like the fact that the UC was trying to send email using the 10.1.10.2 ip addr.

To fix this I needed to go into Exchange and setup a new "Receive connector" pointing to the 10.1.10.2 addr. Once we did that we successfully sent the voicemail notification to my email box.

Still have a call out to TAC on the vpn/routing issues. But using the split subnets on the remote site I managed to get one remote phone to register.

Now 9 more to fix, well once I figure out exactly what I did to fix it!