My previous car was a 2004 MDX, and the fog light mod was a simple 1 wire splice, which took all of 5 minutes.
When I took delivery of my 2016 MDX, I went to the online electrical diagram ($10/day fee, as there is no printed Maintenance Manual or Electrical Troubleshooting Manual anymore - damn you Honda!). The fog light relay is now controlled by a "Relay Control Module" via the Gauge Control Module. According to the Exterior Lights Circuit Diagram #8103, the Gauge Control Module communicates with Relay Control Module via two separate B-Can (ie, multiplex computer wiring) lines from the B-Can transceiver integrated within the Gauge Control Module. Knowing that multiplex lines carry multiple signals through single wires that are very sensitive to short circuits and 'shade tree' rewiring, I stopped trying to figure out how I could rewire my fog light system before I did some serious damage. Tim Allen notwithstanding, I gave up!
Anyone else have a clever workaround?