This may come as a surprise to some, but not to those who have been watching the market closely: the new BMW M5 Touring, the wagon, has generated more demand than the M5 sedan. Both are plug-in hybrids, and BMW has been on a real streak with these models, offering a kind of dual personality that’s hard to resist. The M5, after all, helped define the sports sedan category, with engines that have won awards again and again. There was a time when the M5 made people wonder if the sports car was on its way out. Thankfully, that prediction never came true. The appeal of wagons, or Tourings as BMW calls them, is a fascinating topic. In the US, the station wagon was long seen as a practical family hauler, but in Europe, it’s always been seen as more of the choice for an active lifestyle. For many enthusiasts,..