I did not work *for* UUNET either. However, I did work for Cascade *at*
UUNET as on on-site consultant sometime in 1995. I worked with their
network engineers in analyzing traffic patterns, performing network
design, and looking at network costs. In addition, I followed their
network design closely from 1994-1998.
I can definitely state that UUNET had its own separate Frame Relay and
(later) ATM backbone network that they did not share with Worldcom's
Frame Relay/ATM network. UUNET's L2 switches were directly connected
to T3 TDM and later OC-12 TDM links.