Hi
When you say MPLS, it means you have to select between L2 or L3.
With L3 MPLS, you can get many features (By the provider), and here are some of them:
- Your topology will be Fully Meshed (not point to Point).
- Advanced Security and Routing features can be implemented.
- Many other features like managed Services (Managed Firewall ...).
Now for the VoIP over the WAN, you can have one more feature that is not available on Leased Lines (clear Channel) or Internet which is CoS.
MPLS provider can allocate some of your Total WAN bandwidth and mark is with Real Time CoS then forward all the VoIP traffic over this and the rest for normal data traffic (off course you have to pay more for this CoS).
And that helps to avoid: Jitter, Echo, Lose ... for the Voice Traffic.
Implementation:
You don;t have to worry about it, just the same scenario you described except you forward to the CPE (MPLS Router) exist in each premises and the MPLS provider will take it from there.
Good Luck !!!