We have run a Moodle 2 cluster with automatic failover for 2 years. Theoretically you could use this technique to synchronize two servers in two buildings, but out of the box one is the master-server and one is the slave-server that is synchronized all the time. But you want to synchronize in both directions... so maybe you need three servers: the master server and two slaves you synchronize from the master-server so that the two slaves are acting only as front-end servers to the backend-master-server (in this scenario the back-end-server could only host the sql-database and the two front-ends only apache and Moodle-Php-Code). I guess MNet is still the out of the box solution here. And if bandwidth is the problem, you could synchronize only during night idle time. Our two servers were in the same room and on a fast network. Maybe they were even connected through a dedicated cable for failover-clusters but we lost a lot of performance.
Rosario