On the vehicles we cover with our
Extended Service Plan program (MCU1 and MCU2 S and X vehicles), there's really not anything Tesla can do to prevent us from working on the battery packs.
So far the only snag they've created is with cars that are still connected to Tesla that still have software locked packs. We can change things as needed on the vehicle side, but when the car connects back into Tesla's network it checks in, the server sees a different pack configuration, and then it's like, "Hmm... nope, let's change that." and a bot reaches into the vehicle remotely, modifies the pack configuration, and reboots the car to make the changes effective, all without owner consent or even notification.
We have some ways to mitigate this when needed (usually with salvage cars or oddball situations like noted before), but for the most part as far as we're concerned it's between you and Tesla as far as software locking goes. We won't intervene in that regard as long as Tesla still has an option for you to pay them to release the software lock. On our end, that just means we don't do upgrades on these vehicles. For the extended service plan program, we'll replace the physical pack with a compatible physical pack, and how the car software locks that pack is not our concern.
My issue becomes when someone has a software locked pack, say locked to a 60 with a physical 75 pack. If we upgraded that vehicle to a 100 pack, Tesla's teleforce bot will still try to lock that pack to a 60, instead of just locking out the portion originally locked (~15 kWh). That's not cool. So we just don't do these particular upgrades unless the customer is completely onboard with the caveats required to make it work. I could kind of understand Tesla keeping the 15 kWh locked on the vehicle unless the owner pays Tesla for the additional capacity... but it's just dumb all around.
Honestly the whole software locked hardware thing is completely idiotic as far as I'm concerned.
Anyway, long story short there's very little, if anything, Tesla can do to prevent us from running our service program. We've got both MCU1 and MCU2 cracked well enough that we've prototyped completely custom replacements for them and the car is none the wiser. I don't think there's anyone out there, besides Tesla, who's gotten even close to that.