There's no issue with the initial scan of the plate for the reasons you cited, it's after they scan the plate they don't delete information about vehicles that do not match an alert list compiled by the Mounties.
The BC Privacy Commissionaire stated:
$1:
"Collecting personal information for law enforcement purposes does not extend to retaining information on the suspicionless activities of citizens just in case it may be useful in the future,"
So basically we're slowly becomming a police state, with the RCMP being allowed to keep files on everyone innocent, guilty or in between just like the Stasi, KGB and Gestapo did.
But here's a bit of trivia that I didn't know.
$1:
The program originated in Ireland to deal with the Irish Republican Army.