Comment by harperlee

I stand corrected, what is illegal is to operate them continuously, not to just have them as I simplified above.

"If, for example, you use a continuous recording of the road in which other vehicles' license plates are visible to defend yourself against a traffic ticket, you could be violating data protection, a serious offense that could be punishable by a fine of up to 300,000 euros."

https://www.race.es/camara-para-coche