The MBTA and MassDOT announced they will provide shuttle bus service to Somerville’s 18th annual “What The Fluff” Festival on Sept. 23, while Green Line service to Union Square Station is shut down for the second year in a row, transportation officials said in a public meeting on Tuesday.

Starting this summer, the Green Line is going to look a little different. The first of 30 new Green Line cars has arrived in Newton for testing, a major step in the process of expanding Massachusetts Bay Transportation Authority service north beyond what will be a relocated Lechmere Station, where it currently ends, to Medford. The new cars will be introduced into the system starting in July, even though the new extension won’t open for several more years.

The Massachusetts Bay Transportation Authority hired former Chicago Transit Authority manager John Dalton as the project manager of the $2.3 billion Green Line Extension Project, according to a Monday...