Hello Wilson,
PBR is a good choice to achieve what you want.
Using an extended ACL in the PBR route-map you can define exactly the replication traffic as the only streams that will be sent over the second DS3.
In order to be sure that all other traffic will use the first link you can use two BGP sessions using the physical ip addresses of the two DS3. You will provide a non zero weight to the primary link with the neighbor x.x.x.x weight 500 command so that you have all prefixes installed from neighbor x.x.x.x and backup advertisements via y.y.y.y in the BGP table ready to be used if primary link fails.
If the replication traffic can be characterized as between subnet A1 on site 1 and subnet A2 on DR site you can play with BGP to have these two prefixes installed via the second bgp session via the second DS3 circuit.
You can use a route-map where you selectively increase the weight of prefix A1 to 1000.
access-list 22 permit
route-map replication-traffic permit 10
match ip address 22
set weight 1000
route-map replication-traffic permit 20
the empty second block is to avoid to filter all other prefixes for redundancy purposes
in the router bgp process
neighbor x.x.x.x weight 500
neighbor y.y.y.y route-map replication-traffic in
these must be done on both sides with the correct definition of the A1 prefix(es).
In this way you don't use PBR but every traffic between the subnets is sent via the second DS3.
hope to help
Giuseppe
