As a network administrator (Cisco switches, work with WAN providers, protocol analysis) I have an "area of responsibility" for the customer's VOIP project. The telecom group has primary responsibility for dial plans, voice mail and the monitoring tools that came with the Avaya system, but the traffic goes over the data network, so at some point I expect to be involved.
QoS has been implemented. I have not yet received any formal training, and most of the training offerings I have seen have had more to do with VOIP administration than data network related issues.