I have done this through a T1 connection and while the patching is slow, as long as the connection is not really needed for anything else it is possible. I have noticed when attempting this that in addition to taking a long time (because of the patch copying) I typically have to remediate a second time as Update Manager will time out. Another note is that if you using monitoring (say Nagios) in the primary DC to check on the remote site, you will want to disable notifications to the remote site as Update Manage will hog all the bandwidth. Due to these factors, I schedule updates during the night or over the weekend.