for my next comment, I want to consider what we've heard in the thread. 1) NASCAR is being cagey on details. 2) The manufacturers are clambering for it. 3) A significant amount of development has gone in a spec car that leverages core aspects of NASCAR's "IP".
I spent most of the time, thinking about: if this had to be used, where would it make sense based on the expected time limitations?
My mind jumped to the idea that (afterall) NASCAR owns GrandAm. This 'CUPEV' would probably be a reasonable replacement for TCR. And as a support series, there'd be a way to pop there shorter races around the practice/qualifying schedules.
Along the same lines, the same cars and drivers could potentially be added to a number of 'short track' days on the NASCAR calendar (Martinsville, Bristol, ?), as well as a couple of other 'experimental' venues (ala Rose Bowl, Chicago Street Circuit).
That would be a reasonable number of dates, and a wide cross-section of venues, fans, and "activations" (if I'm getting my 2010's marketing terminology correct).
With a portable generator, these things should be able to charge anywhere between 250 and 500kW; which means the pack should be able to charge between 10 and 20mins. Too slow for a pitstop, but more than enough time to get done between sessions of 'other stuff'. Unless someone at NASCAR is crazy enough to try and split the pack, and figure out a way to plug two 500kW chargers at the same time. 
I reckon some combination of the above is likely. Hopefully someone over there has the foresight to realize this series needs to be at GrandAm and NASCAR races.
and that gets to the really interesting "why?" question.
in case it wasn't clear, NASCAR is way behind the curve on hybrid and EV racing. If they sit around ignoring it, they're going to have a lot of the rules for GrandAm dictated to them by LeMans/FIA (who are almost certainly going to be forced into Hybrid/EV rulesets because of the environment around the {physical, legal, political, cultural}), because they won't have any internal expertise to draw on. And, there's only so many times you can pull on your upper cheek, say "mon oeil", and stick out one's tongue before you're ignored altogether.
also, NASCAR is losing fans/viewership. they need something else to draw in and excite people. this might be it, especially as a number of younger people are away of EVs and their performance capabilities (in part thanks to Garrett Mitchell / BoostedBoiz, etc). ironically, in some ways, their current "stage race" / "mandatory pitstops" format while probably eventually dovetail really well into a NASCAR-EVCUP format, eventually, where the race stops every 30mins for a tire-change/charge. But, I reckon it'll be ~10years before the batteries are there to go that long at 600-700kW, not to mention figuring out how to charge 400-500kW in 5minutes. None of that, though, is possible if they don't start now with baby steps and getting familiar/expertise in how these systems work... and that's before one even gets around to dealing with how much easier it is to spec-race an EV.
final part of the "why!?" - Manufacturers
Chevy and Ford, need this. I realize there's a lot of resistance {heh} to EV's here. But, there's a lot of markets outside the US (which is total easily outweigh our market here) where EV's a more than priority. they're a necessity. Plus, over here, Ford and Chevy need to wipe clear some missteps when it comes to EV's, and have a better chance of "telling the story" of EV's to a group of buyers who will go out of there way to avoid it at all costs. The more EV's they can sell here, the less likely they are to become the Jaguar, British Leyland, etc of the 21st century. So, adding some EV racing to NASCAR is an unparalled avenue for bridging that gap, educating, and informing.
I'm curious to follow this development, at a slight distance. Even though I'm excited by the possibilities EV's bring to motorsports... I've learned to be cautious of NASCAR's iron-ham hand.
but, "thus just, like, [my] opinion... man"
standard buffalo caveats: lector, emptor, oculus, mathematica, iirc, ymmv, etc.
