Not the written rules but the spirit. They got a waver for a wider body, a v8 engine from another BMW and a transaxel rear end. They were politely told by the ACO to not request a Le Mans entry. The rules were written in GTE to be production based and to have road relevancy. That car is basically nothing like a stock Z4. I'll save you from the rest of my rant on this car and the GTE rules.
Great shot by the way. You are by far the best photographer I've seen when it comes to shooting races at Laguna Seca.
Yup! BMW is the king of exemptions. Even when they had the wider M3, they still cheated and mounted the engine way further back than in the production car. And lets not forget when they did a V8 in the E46.
Regardless, this is still a very good looking car, and excellent panning shot!