For those of you outside the USA
If you have a GT not made for the NA market, would you take a look behind the bumper cover near the left side exhaust pipe and see if there are a couple of plugs tucked back up in there? They should have dummy caps in them to protect the pins/sockets. These are for installing the factory trailer wiring harness. If those exist, there should be another one under the floor of the trunk to capture the trailer interface module.
I'm curious which markets have this prep in their harness. I have an OEM kit that is designed to plug into one so prepped, but it does me little good, since those plugs don't exist in our harness, and the NA BMW group can't get the prep package (nor do they make any towing options available on the GT here). I've been trying to get the pinout of the module, but to no avail, so I could cobble up a harness myself.
I'm going to be in the UK on Monday, and may try to either pick up an interface harness kit and maybe look at a vehicle there myself. I'm hoping, if I buy one there, it will work in my vehicle as I'd really like to turn off the PDC blaring at me when carrying a bike rack. I'll pick up a trailer plug so I can make an adapter should I want to actually tow a US trailer and need to connect its lights.
If I had a bicycle rather than a recumbent trike, I'd bite the bullet and get their roof-mounted system (which is available here), but that makes it impossible to drive into the garage or even park near my garage since there's an elevated deck above with limited height. It's just so much quieter and easier to just tuck it on behind, but that means you live with the PDC issue.