MTA

The Boston Metropolitan Transit Authority was the predecessor of the modern Massachusetts Bay Transportation Authority. Until the mid-1960's, the MTA managed Boston's streetcar and subway system.

Mail Transport Agent. A server that makes sure mail gets to the right place.
The most famous is sendmail, but others
include postfix, smail, the sublime qmail Microsoft Exchange and many many more.

Humorous folk song written to protest a fare increase to ride the Boston Metropolitan Transit Authority subway, most memorably performed by the Kingston Trio. The protagonist pays his dime to get on the subway, but when he tries to get off he's told that the fare has gone up by a nickel; fishing in his pocket he finds that he can't afford to leave the train.

Chorus:

Well, did he ever return? No, he never returned, and his fate is still unlearned.
(What a pity! Poor ole Charlie. Shame and scandal. He may ride forever. Just like Paul Revere.)
He may ride forever 'neath the streets of Boston. He's the man who never returned.

Major Trading Area

In telecommunications, a group of counties that represent a geographic area of common business interests and relationships. A BTA, or Basic Trading Area, is a subset of an MTA. The FCC awards cellular licenses for a particular MTA or BTA, making it nearly impossible for any one company to provide comprehensive nationwide coverage.