I had a little discussion with Ed Hamrick, the maker of VueScan about his RAW format. Basically what he said is that it is a normal TIFF file and that there is no point in editing it with Adobe Camera RAW which BTW is not able to open his TIFF file.
Here is his explanation:
The reason Adobe Camera RAW doesn't read TIFF files is because there's
no reason for it to do this. The whole point of Adobe Camera RAW is to take
images from a color filter array (i.e. one color per pixel) and interpolate this
into a three colors per pixel data source.
Scanners already produce 3 colors per pixel and VueScan's raw files have
3 colors per pixel.
The people at Adobe could read VueScan's raw files with about 5 minutes
work, and the files are just normal TIFF files that they could easily read. The
reason they don't do this is because it would be a complete waste of time - the
VueScan raw files are already 3 colors per pixel.
If anyone want to take a peak at a RAW file from VueScan, just let me know and I will do a scan. You have to pay to do that since it is not available in the demo version.