I think this is unlikely since plates are alphanumeric. Although I suppose if you faked an image of a plate it's possible you could cause problems for a plate scanner.

[1');DROP TABLE tickets; --]

(Damn. Way too many letters...)

Relevant XKCD:

https://xkcd.com/327/

There was someone who not too long ago fixed an SQL injecction to his front bumper and it managed to break the automated toll collection system.