When I shoot with an older back like a P25/H25/H20 etc...using C1 3.78 for shooting (as it is much faster than C16x), It saves the file to the computer. LR 3 and 4 ONLY see IIQ files and NOT TIF. It does see the thumbnail TIF, but that's just a low res preview. I too have no idea WHY they did this....Even Canon on the 1Ds did this.
fyi, shooting with C1 3.78 the image almost instantly pops up on a WinXp machine and sharp(also the preview Zoom/detail on the 3.78 is VERY useful, as with the way the pixels are arranged, you can tell if its going to be sharp or not. (I can elaborate if one cares). So you dont have to wait for the large image to be fully sharp.
Shooting in C16 on same machine is about 12seconds. Shooting C1 6 on a Quad i7 Win7-64bit 16GB Ram with SSD, still takes a good few seconds!