[bogomipz]

>"Judging by historical bike registration programs."

Well most bicycle licensing programs ended decades ago. I think it would be far more efficient and cheaper to implement such a system a now.

>"Technically speaking, what ID would be visible to traffic cameras?"

A small RFID transponder on the bike and an antenna mounted over the bike lane at an intersection. The antenna activates the transponder. This is similar to how the EZ-Pass toll system works in the US. Cars come in many shapes and sizes too and it works just fine .