What does MTR stand for when speaking of the Guangzhou–Kowloon Through Train's operating system?
Guangzhou–Kowloon Through Train: The Guangzhou–Kowloon Through Train () is an inter-city railway service between Hong Kong and Guangzhou jointly operated by the MTR Corporation of Hong Kong and the Ministry of Railways of the People's Republic of China. MTR Corporation:  MTR runs Hong Kong's Mass Transit Railway (MTR), and is also a major property developer and landlord in Hong Kong.
Mass Transit Railway