The CLE had the XG shutter button - that is the prominent (and wear prone) part where you can plug in the XG equivalent with minor tweaking. Beyond that, much of the similarities are only exploitable by a skilled service technician. Once you break down the shutter or electronics into their individual parts, about 90% of the small parts are common to them, but due to the difference in size, they do not share entire modular components beyond the already mentioned shutter button/time knob - module dimensions and solder point positions are different (and the CLE has a entirely different focusing and AE system in any case).
In a nutshell, a XG is a good source for small parts for the CLE, but it will not supply you with a drop in transport mechanism or shutter. But as far as the most common electronics failure (the wiper contacts under the time knob) is concerned, you would be lucky...