CJ,
I have never used an ATV to recover an Elk. With the exception of 2 that have been hauled out on horses, every other Elk that I have had the fortune (mis-fortune??) to be involved in the recovery of has came out on a back pack. I could probably spend some time counting, but I am sure it is between 20-30 critters we have hauled out in this manner, out of our Elk camp.
Right now, in our camp, we are debating the wait until 40 or 45 before we resort to horses, but so far we haven't wasted the time bringing them up, and we have access to them and a couple of mules. It is just easier to go get the meat with a pack frame.