Since the engineer is talking to you (a rarity in itself) try to get him to consider seeking a balance between false positives and bicycle detection. It's possible that some fine tuning can work acceptably for all interests..

The answer might involve tuning and aiming to a standard "sweet spot" which bicycles can move into to be read. If that works, painting a marker on the pavement would be the next step.

If dialog and experimantation doesn't yield a solution, then it's a matter of speaking to the city council (or whoever's in charge) and seeing if they'll give bicycle needs some priority and build it into the plan.