The facility is available free to all first class customers using the lounges, not just T-Mobile users, said Virgin.
But first and second class Virgin Trains customers will have to continue to wait to get Wi-Fi access on Virgin trains, as well as a simple and reliable mobile phone signal.
Currently, the metal thickness of the carriages on the new Virgin trains and the small size of the carriage windows, prevents passengers getting a reliable mobile phone signal that does not drop in the middle of a conversation.
This means that users of mobile data cards in laptops also cannot work while travelling.
Virgin Trains new product development manager Victoria Mawson said, "We intend to roll out Wi-Fi across our trains later this year."
Virgin Trains says it is also improving the mobile phone reception onboard its trains. Upgraded trains provide the same level of reception inside the train, as is available outside, it says.
The first 16 upgraded trains are already in service and will soon be easily identifiable by special labels on mobile phone and laptop charging points located at seats.
Virgin has been struggling with mobile signal problems since the trains were introduced to the West Coast line and elsewhere. Four years ago, Virgin told Computer Weekly that it was tackling the problem.
Both first and second class passengers on the East Coast line, run by National Express, now get free Wi-Fi access on trains.