This was discussed many years ago in Elvis Monthly and other publications.
A reporter at the NYC press conference asked Elvis why they filmed in Boston rather than New York. Perplexed, Elvis passed the question over to the Colonel.
What the reporter presumably meant to say was Buffalo, which, as you know, is also in New York. Hence the confusion. The Buffalo show on April 5 was filmed by Robert Abel with just a small Sony camera to get a feel for the performance, in readiness for the upcoming April shows.
There was a theory going around years ago that the film footage of An American Trilogy (as featured in This Is Elvis) was actually from the Buffalo Sony camera footage: one angle, the colour isn't all that great. And I'm talking here about the footage itself - not the actual sound. Trilogy from TIE may have been overdubbed with the sound from Hampton Roads (evening show) from April 9 as Abel's camera would not have been able to capture sound in releasable quality. However, the TIE footage belies that theory. It's from Hampton. I do wonder why they only used one angle for Trilogy though. Maybe for cinematic effect?
And MSG was not filmed presumably because they had just filmed several shows in April. But what a pity they didn't film in MSG: Elvis was slimmer, certainly brighter than in April. The June shows were better overall too.
An Elvis On Tour based around the June tour and the MSG shows would have been something all right!
Cheers for that