According to the BBC, the arrest was executed by the Northumbria Police with the support of the Met's Police Central eCrime Unit.
The youngster has been detained and is currently being questioned about alleged offenses under the Computer Misuse Act 1990. His computer equipment has been seized and is being examined by the police's digital forensic experts.
MLT's Twitter account has been silent since the arrest, so it is believed that the police have arrested the right man.
TeamPoison is a well known group that has taken responsibility for a great number of hacks, including the ones targeting T-Mobile Web servers and UN's servers, as well as a DDoS attack against Scotland Yard's Anti-Terrorist Hotline and the alleged compromise of the Metropolitan Police's phone system, for which it's alleged leader was arrested in April.