If dashcams are then so are Tesla's and bigger issue with Tesla is if any of this footage leaves the car. Especially if it goes outside the EU like autopilot disengagements.
This isn't something tne Tesla owner can sign in the ToS because the people in the footage are others. Tesla probably uses the excuse that you the operator are in violation not them but then again a Tesla owner has only limited control over this. I can legally buy a surveillance camera but it is my responsibility to use it legally.
But why do you think dashcams are illegal in the EU?
It's been ruled by multiple courts in the EU that dashcam recordings can be done legally because everyone is aware that they might be recorded in traffic at any time (e.g. by traffic cameras). That said, you have to comply with some restrictions. For example, you are probably not allowed to publish these recordings on Youtube. But they can definitely be used as legal evidence in court.
Secondly, I don't think Tesla's dashcam footage leaves the car in the EU (unless there is an accident, perhaps).
As far as I know, they don't even transmit or save any recording unless there is an accident or the user presses a button to save the footage into a USB drive inside the car.
In the accident scenario, it is quite clear that it's legal to keep this recording, because these can be used in court as legal evidence. As far as I know, there are many situations in which you are not allowed to film someone or something in the EU in general, but you are allowed to do so if you intend to use it as legal evidence, as that purpose trumps the other privacy concerns.
In the "user presses a button" scenario, it would be the user's responsibility to make sure that the recording is used legally. But again, if the user does not publish the recording and is only filming traffic, this is quite likely to be legal, especially if you only use it in reasonable scenarios (such as recording an accident in which you are not involved, or someone driving drunkenly).
It's not like anyone is going to be pressing the button every 10 minutes. And even if they were, it would be their responsibility to make sure it's legal to do so. It wouldn't be dashcams themselves that are illegal, but rather, what you do with them and the saved footage (if there's any).
Edit: I'm talking about the normal usage of the dashcams, not the Sentry mode functionality which has additional concerns (as you're not recording traffic, but rather people in the immediate surroundings of the car, when the car detects movement around it). As far as I know, courts have already decided that it's legal to have Sentry mode as well, but Tesla was required to warn users that they have to comply with data protection regulations when they use this functionality.
That said, I'm not sure what are the exact requirements for using Sentry mode legally.
There is one potential way it may be getting used which would probably be legal.
Years ago, before smart phones became ubiquitous, I worked for a company that had a contract to provide kiosks containing travel planning software to bus and rail stations. As part of this, one of the jobs I had to do was create a method of recording information from an onboard camera in the case of the kiosk being vandalised.
How it worked is I made a rolling cache of the last 30 seconds of video; this was never saved unless an onboard "shock sensor" was activated. If the shock sensor was activated then I would save the last 30 seconds of video plus another minute or so. This could then be used as evidence by the police to help catch the vandals.
I have no insight into how the Sentry Mode functionality works, but it could very easily use a similar sensor to car alarms to only actually save the recorded video if there is some sort of "impact" on the car.
This isn't something tne Tesla owner can sign in the ToS because the people in the footage are others. Tesla probably uses the excuse that you the operator are in violation not them but then again a Tesla owner has only limited control over this. I can legally buy a surveillance camera but it is my responsibility to use it legally.