I ran across this on the cisco site and I wondering if it was possiable with two 2851's? The part that is most interesting to me is this part of the config (this looks like what allows the use of the y-cable)
Any other ideas on how to have a redundant border router with a T1
Based on reading the link, i would suggest that the y cable solution is for the 1941 mobile wireless router (mwr). But it wourld might be worth trolling around. I took a look, and it appears only to be in the IP-RAN feature set, for the 1941.
As to your other question. with only one T-1, your're options are limited at best. what redundancy problem can you afford to solve? circuit? router ?
Thats kind of what I thought sadly. Unless we can figure out a way to use a single T1 we might just have to order another T1 and connect a router to each.