Hi,
In this case it is not actually about BGP or not. For redundancy purposes you could very well use OSPF. It has faster convergence if you stick to the default parameters. (I am actually no fan of tuning convergense parameteres). You should agree with your provider, and for the MPLS VPN PE routers they run BGP. BGP is primarly a routing protocol for connecting ISP's. (autonomous systems). An for MPLS providers M-BGP (multiprotocol BGP) keeps track of the vrf's
So it actually only depends on your budget.
Is the branch office connectivity so important that it justifies a backup link.
The answer to that it is only you that can answer :)
HTH
Regards,
Bjornarsb