The recording system is at least as important as the camera. You need one with a high resolution capture image so the plates are legible. A friend and I put together a PC with an AverMedia capture card that came with software to read and record plate numbers into a document.
I use a high-end Sony camera with a zoom lens, but it misses a lot of tags. If they're moving too fast or if there's too much light shining on the lens the tag can't be read. I'm thinking of getting a 3 megapixel IP camera which will work with less light and gives a much higher resolution image than any of the usual RCA or BNC cabled cameras.
There are speed bump cameras that seem ideal, but I'm sure in Canada it would spend a lot of time covered in snow.
