IPSec on Cable + Direct route on T1

[ctxspy]

Hello Everyone,

I did a search but couldn't find an answer to this specific setup.

I have a P2P T1 as our main line, and a Cable modem as a backup.

Right now I have a MANUAL setup, where I have to unplug the T1
router when it goes down, and plug in the VPN router. (They have the
same IP to assist w/changing default routes etc.)

Anyway, I'd like to somehow set up automatic failover so it is transparent
to the end users.

I see a lot about basically dual "WAN", but in my situation one connection (cable)
is a true WAN while the other is really a direct connection to the destination network.

Is what i'm asking possible?  If so, can you give a basic idea of how to do it?

Thanks,
Tomaj