I think the term "interconnect" is fairly generic. I have often heard
some of the providers refer to the MAEs and NAPs as "public interconnects"...
However, I think folks use the term "MAE" and "NAP" to refer to different
implementations of a "public interconnect"... It is probably an
oversimplification to say they are all the same thing.
When the TLA's are expanded into their actual meanings, Metropolitan Area
Exchange, and Network Access Point, there does not appear to be a great deal
of difference between the two, except that one is a term that MFS Datanet
started, and the other is one that the government sited as the term for the
exchanges they were helping to fund/promote.
I tend to agree with what you say about implentation, but there are exceptions
to every rule (The Sprint NAP uses MAE-like technology). The Tucson NAP
uses a mixture of NAP-like and MAE-like ideas, but also is not funded by the
NSF. The choice of naming had little to do with technical implementation
style, that much is certain.
As for the original topic, other regional exchanges, perhaps Eric at
Structured would like to talk about the Northwest Internet eXchange? (NIX)