Hello all,
The Voip Standards and VoMPLS do not compete; they are ships in the night so to speak.
You will need Voip Standards in all Lans, and Mans,and Telcointerface.
Where these networks contact a WAN you may have to interface to MPLS where the Voip channels will be assigned into a FEC and a tunnel and treated with QoS paramters for real-time messages.
To see more about MPLS please see Convergedigest.com.