I have done lots of etherchanneling in data centers. But I have never tried it as a failover topology between two sites. In the LAN it works great for the additional bandwidth and for failover. i.e. if one of the *ethernet in the bundle goes out the other members of the etherchannel just keep chugging along.
So imagine site A with Cat2948 2/49 ethernet over fiber to carrier 1 and 2/50 ethernet over fiber to carrier 2. Site B 25 miles away is setup the same. Ports 2/49 and 2/50 are configured as an etherchannel bundle. On the surface it seems like this should work. But might I be missing something perhaps with the two carriers, timing, the distance or other?