The Flight envelope of the 767 was designed for normal operations. I have flown the 767 to those limits of both 360 knots and M0.86 without a problem because that is what the envelope is for. A normal operating envelope. When a 767 climbs we start at an airspeed of around 290 knots and at around 28000 feet transition to a Mach number climb of about .8M. The reverse is done on descent. The aircraft is easily controllable throughout this envelope.
The author of this video, a guy called Balsamo who has apparently been caught out photoshopping a fake flight envelope diagram in order to "prove" his hypothesis, seems to have not much idea of the mach number/IAS relationship and what it means. The Mach number limit on the 767 is an aerodynamic limit, not a structural one. Above that Mach Number the shock waves that would have begun to form over the wing begin to affect lift and stall the wing, which is called a high speed stall. This happens at any altitude that Mach 0.86 can be achieved in a 767, because it is purely dependent on the design of the aircraft and the wing in particular. A 747, which has a different designed wing has a MMO of M0.92.
The 360 knots IAS is an envelope limit. The aircraft will not break up necessarily if you exceed it, but it has been assessed as the maximum speed needed for normal operations and has been cleared by Boeing test pilots for all those normal operations. I do not know what IAS will result in the breakup, but it is a theoretical limit and would be far above 360 Knots. The Mach number that Flight 175 achieved at 513 knots at approx 1000 feet was about M0.78, so it was below the aerodynamic limit of M0.86.
So the only two questions are:
1. Does the 767 have the thrust available to fly that fast at 513 KIAS at 1000 feet? and
2. Would the aerodynamic loads of flying at that speed and height cause break-up of the airframe?
Q1. In my opinion, most definitely. The aircraft has large amounts of excess thrust at low altitude.
Q2. I cannot answer that question from any data I have seen, but if you accept that flight 175 was an unmodified 767, apparently it can.
Boeing build very strong airplanes. Just ask the passengers on the 747SP that China Airlines sent through Mach One after a mishandled engine failure at FL410. The 747 was taken through Mach One during its test program by Boeing and the British CAA.
http://en.wikipedia.org/wiki/China_Airlines_Flight_006