Few points from my side for your query
Access Link should be considered based on whether we are going for MPLS L3 VPN or MPLS L2 VPN Soilution
MPLS L3 VPN from my understanding is independent of Access Media but the Access Media will definitely put different hardware requirements for your Customer Edge Router
The Access Link Type and Bandwidth would vary depending upon the BW requirements for the network. The T1/T3 or a Subrate T3 Access Links would be a choice when we have BW requirements in that range(<45 Megs)
Using FE as an Acces link would require SP to provide Colocation Services or rather go for spanning a Fiber out from their Colo and deploying Optical Mux at Customer Premises and again suitable for BW requirements more than 45 Megs
MPLS L2 VPN
Ethernet is the choice for taking MPLS L2 VPN Services to connect your different branches in a point-to-multipoint fashion using VPLS at SP end.
You can go through the Cisco Doc - "Layer 3 MPLS VPN Enterprise Consumer Guide" which should help you gain more insight for choosing the PE-CE Routing Protocol and other points to consider for an MPLS L3 VPN Service.
Thats from my understanding. Hope you will get more good advises on this.