Yes, cut and cover is hugely expensive and has been suggested and rejected many times over.
Getting way off the Type 9 topic now (I apologize, I've been a part of that), but in an attempt to bring it back, I'll just say that the fact that Type 9s are equipped with plug doors is not a particularly compelling argument for not running these cars in street running service. Such cars are operated in street running all over the world every day - in fact it has been done in Boston before, with the Boeing LRVs, although that era was somewhat brief since another thin argument was made "The Boeing cars have a high voltage equipment cabinet under the floor and if an auto T-boned a streetcar at that exact spot..."
Getting way off the Type 9 topic now (I apologize, I've been a part of that), but in an attempt to bring it back, I'll just say that the fact that Type 9s are equipped with plug doors is not a particularly compelling argument for not running these cars in street running service. Such cars are operated in street running all over the world every day - in fact it has been done in Boston before, with the Boeing LRVs, although that era was somewhat brief since another thin argument was made "The Boeing cars have a high voltage equipment cabinet under the floor and if an auto T-boned a streetcar at that exact spot..."