Yes it is possible, but may not be feasible. We do something similar in our company, backing up data of a remote office to one of our servers in HQ. We have a 24/7 VPN connection between the sites and we do this via normal mapped network drive. It works, but we only have approx 5Gb data to backup.
So if you have large amount of data to backup then an ordinary broadband line may not be sufficient. Perhaps you can get a leased line or T1 or whatever between the sites. However, this shouldn't be your only backup for the main server, this should be treated as a second backup "just in case".