On a previous assignment I wasted some time worrying about interworking Ethernet Private Lines in the access/aggregation layer and MPLS pseudowires in the core when carrying end-to-end isochronous services such as voice and TV.
Just a reminder to self how I belatedly realised that a much better solution is to run MPLS pseudowires edge-to-edge from the CLE (customer located equipment). Of course, this means that the CLE must be MPLS-capable.
Important to ensure that the CoS indicators in the payload headers are replicated in the MPLS Exp bits and the Ethernet 802.1p indicators across the switched Ethernet network.
Also need to worry about how end-to-end protection is to be ensured (e.g. is RSTP good enough in the Ethernet part of the network? What are the alternatives?).
A good summary, although a few years old, here.