Tempted to say almost all of them, but the major ones in ON for sure. The problem is that back when it was just the SR, and the Z06 was but a dream, and any other variation was unknown, most dealers (probably 95% of them) maintained 2 lists, a SR list and an everything else other than the SR list. This mixed in the Z06, E-Ray, ZR1 and Zora folks all together. The dealers simply did not know how future allocations for these models would be handled.
Fast forward to today, and I think the dealers are about to find out, and what I am hoping will happen (key word hoping), is that GM allocates separately between the E-Ray and Z06, meaning they do not have to pick between one or the other on a non SR allocation. And if that happens, then hopefully (there is that word again), the dealers will take the time to call everyone on their non SR list, and ask them which model they want, and split out the Z06 folks from the E-Ray folks, which will make things a little easier for everyone, and give people their actual spot on the list (instead of being say #100 on a mixed list, could be #30 on an E-Ray list).
To answer your question, the answer is quite obvious. Too many people were interested in the Z06, and when the rumours started become believable, and some of the info confirmed as fact, that interest only increased the desire for the car, so more people piled onto the non SR lists. Those dealers then sat back and did some math, and said if I am only going to get 1-2 allocations for this car a month, at best, and I already have 50-100 people on my non SR list already, there is no way I am going to be able to deliver this car to someone after a period of 4-8 years to the people at the bottom of that list, so why continue to take deposits if the dealer cannot deliver the car in a reasonable timeframe. So most of the dealers (I say most but could be many), have CLOSED their non SR (Z06/E-Ray/...) lists, one cannot add their name to it any longer.
I can confirm the above as fact, as the dealers I am dealing with both have closed lists. Perhaps I may try to convince one of them to still add my name to their list, with the hope that they will get my upcoming (new) SR as a trade-in to add to their marked-up inventory to make some good cash off of it. So there may be some incentive for them to do me the favour (I hope). I am also hoping at some future point, the SR holds it's value, and my SR trade-in will yield a decent enough return to make the higher cost of the E-Ray a little more palatable .
So long story short, if most people think you can just walk into a dealer and drop some cash down for an E-Ray on some accessible open list, they are dreaming, unless you live in a small town with a small dealer who gets 3-5 of these specialized models a year, in which case you will be #x of 10 and will wait maybe 2-3 years instead of 3-5. Yet for all the major dealers I know of in ON, and likely most in QC, closed lists. If I am wrong, please let me know so I am informed as to where I should be targeting my future E-Ray deposit