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They have to say that because almost certainly they've used everyone's data in some fashion that makes it almost impossible to separate out. If they've got a count of everyone who used Road X and your ride(s) are included in that count, they're technically using your data but there's no way for them to remove you numbers from the count if they're only storing a total. So, saying they will have some anonymous data left over is a catch all for stuff like this. Sure, they could take the piss and just maintain everything but if they were found out the fines are large.
They specifically say not everything will be removed, and they'll keep using some data without having it associated with your name.
I don't actually mind though, that was not the point.