I don't have a fully loaded Regal, but I know daytime running lights were an option on 89 Regal GS when they first came out as an option. Do you have a headlight switch that controls the fog lamps? Like if you have a wiring diagram you can see if the headlights and fog lights work on the same circuit. I would bet you have a blown circuit breaker if you say the wiring is good. First check all fuses and make sure they are good in the fuse box located in the glovebox. If you find any blown that might be a good easy fix.
I had one shop diagnose no headlights turning on on mine. It turned out to be the circuit breaker relay under the glovebox was blown. Which I had no idea I had one. The whole time I was looking at the headlight switch.