There's an op-ed on Planetizen discussing the MTA in Los Angeles as a stealth development agency. I don't know if I would go that far. I think most people know they have eminent domain power and that they can redevelop property close to the stations but it's not as powerful as say the rail agencies in Hong Kong or Japan.
If any transportation agency was going to be a true development agency it would have even more power to land bank and develop properties than is currently allowed in the United States. In fact, this is how transportation worked during the streetcar era. Property was the main money maker rather than transportation, the transportation was the hook. But it created some great places such as the inner ring suburbs we now love. I would love to see transit agencies have more power to develop, but surely that won't happen because of property rights activism among other barriers.