There's an explanation for the aspect ratio switching here
. Apparently the film was shot 1.78:1 open matte, framed for 2.39:1 display (2.35:1 on BD). The IMAX version switched back and forth for certain scenes and apparently the BD used that source, also apparently used by VUDU. That article lists the scenes shown in 1.78:1.
I recall at least one other film shot that way, Man on Fire
(2004 Tony Scott remake w/Denzel Washington in the role of Creasy). The DVD was 2.35:1 but it was shown 1.78:1 on premium cable; I compared the two and found out it was the 2.35:1 which was "cropped"
. The crew and director have to be very careful when they use this technique, to make sure that cables, boom mikes, etc aren't visible in the version without mattes.