Earlier today I was researching ECW and MrSID files for a non-MapPoint project. This was just a preliminary overview and I didn't get into much detail except find out what they were and could we/my client support them.
re. your question:
The quick answer is no. You cannot import aerial photograph images (of any kind) into MapPoint.
However, I remember someone on the Usenet saying that they managed to get an imported aerial photo effect by importing lots of different pushpin images and tiling them at a suitable spacing. The problem with this is that it only works at one zoom level.
If your data is relatively coarse, you could plot it with polygons. I would expect MapPoint to be very slow though.
A similar technique is used by my GridImp product:
http://www.winwaed.com/products/mappoint/gridimp.shtml
but this plots data that is typically a lot coarser than aerial imagery!!
(my earthquake hazard samples use data on a 0.1deg grid)
If you are looking for someone to do some ECW coding, I would be interested. It looks an interesting format, and the shared experience with this other future project would be beneficial for all.
Richard