Let's look at a hypothetical situation. ISP1 peers at MAE-E and
buys transit from MCI there. Now they ask Sprint to peer with them. Let's
look at how they reach sites on the west coast.
This is a violation of the rules of Mae-East: it is not to be used for
customer connections. ISP1 must have a private connection to MCI.
True. Serves me right for composing a quick example. Let's change
the example to say they get the transit through a private T3.
So ISP1 peers at MAE-East and has a private serial circuit to MCI
(or someone elses) router at the MAE (not using MAE infrastructure).
Same result. And same result even if ISP1 peers at the MAE and sends
all its traffic to any MCI site 'near' (in network terms) MAE-East,
ust as long as MCI gives the traffic to Sprint there.