It's really pretty easy. Getting the actual animation data across is the tricky
part. You can export the animation curves from Maya using the MOVE format (make
sure you bake channels first!), modify the text file in excel so that the columns
correspond to XSI .RAW file format, and make sure to include the proper file
header. Once you are sure that the animation curves are identical (simply look
at the channel box in Maya and compare the numbers in the transformation fields
in XSI), you have to do a couple of things:
1. Make sure that you are masuring the field of view the same way (horizontal or vertical) in both Maya and XSI. In Maya, modify the "film fit" attribute of the camera to match the horizontal / vertical tab in the property editor of your camera in XSI.
2. Make sure your field of view is identical for both cameras.
3. Make sure that your resolution matches in both packages. I have not gotten a pixel aspect ratio other than 1 to work properly. When dealing with broadcast, use 720x540, with a pixel aspect of 1. I think that Maya and XSI squeeze the images in opposite directions when the pixel aspect is set to anything other than 1. Make sure that your device aspect ratio is identical in both packages. This is found in Maya in the Render Globals, and in XSI under the render properties. In XSI, it's called "picture ratio".
4. Make sure that the picture ratio for your camera in XSI is set to the same picture ratio that you just set in the render options. (For 720x540, that would be 1.333)
5. To be on the safe side, set the Camera Aperture options for your Maya camera to 1 and 1. Also set the film aspect ratio to 1. This might mess up your angle of view setting, just set it back to the desired number.