For anyone else wondering, I managed to dig up some more info and figured I may as well post it here. I recently spoke to the president and VP of the WCMA as well as another source familiar with the situation.
The concern is indeed battery fires, and I'm told the insurance company won't cover damage to the venue due to a battery fire. For those unaware, the various breeds of lithium batteries found in electric and hybrid vehicles tend to burn hotter and are harder to put out compared to say a gasoline fire.
This same insurance company apparently insures all motorsport across Canada. GDS Canada is working on a set of requirements for EVs (including procedures for dealing with a fire) but all discussions are happening behind closed doors. I'm told that it will likely be some time before these requirements are published, and then it will be up to each province to decide whether they want to adhere to these regulations or just bar EVs from competition.
So unfortunately for me, I gambled and lost when I decided to convert my bike-engined car to electric. Dang.
One other point for anyone else who is sidelined with their EV, I guess BC is still allowing them to compete despite the lack of insurance for damage to the venue from a fire. You could drive out to Kelowna to catch come autocross there... at least for now.