A top regulator in the Baker administration is accusing the MBTA of improperly rushing through the sale of T land that Wynn Resorts wants to use for the entrance to the $1.7 billion casino complex it plans to build in Everett. In an e-mail to representatives of the T and Wynn, Deirdre Buckley, director of the Executive Office of Energy and Environmental Affairs, said that last month’s $6 million sale of 1.75 acres violated state regulations.