DVCPRO-HD records either 960x720, or 1440x1080. There is no setting to make the recording format record 1280x720. If you shoot 720p on any DVCPRO-HD camera, it will always be recorded as 960x720.
It is an anamorphic format with non-square pixels, when displayed correctly using the 16:9 aspect ratio, you wind up with 1280x720 square pixels. It should intercut fine with images recorded at 1280x720.
Yes - because it's not 960x720 "square pixels", it's 960x720 with a pixel aspect ratio of 1.333:1. Video editing programs know how to deal with it and turn it into 1280x720 when editing.
In other words, if you were to view it at 960x720 with square pixels, it would appear squished horizontally. The pixel aspect ratio stretches it out to the equivalent of 1280x720 in square pixels.