Those "trolleys" you refer to had not changed a whit until Katrina. The red ones were on a new line. The old ones still ran along St. Charles to the Quarter and back past RiverBend on Carrollton. But I have never heard any New Orleanian call them a "trolley". Trolleys in my understanding are like the cars in San Francisco, not powered by electricity overhead like the ones in NO. Only the tourists call them trolleys.
I hope they are NEVER retired and replaced with new ones, even if they are built to look the same. They wouldn't BE the same.