Here’s the bill that was passed, the original legislation was engrossed into “An Act relative to Massachusetts’s transportation resources and climate”:

https://malegislature.gov/Bills/192/H5151

Regulations on use are described beginning in Section 14 on line 1360, continuing through Section 21. In addition to the general inclusion of class 1 and class 2 e-bikes in regulations regarding non-e bikes, there are these distinctions:

1) “electric bicycles shall not be ridden or operated on sidewalks.”

2) “A municipality, local authority or state agency with jurisdiction over a bike path or bikeway after public notice and a public hearing may adopt ordinances or regulations prohibiting or otherwise regulating the operation of electric bicycles on such paths, including, but not limited to, the imposition of speed limits.”

3) “An electric bicycle shall not be operated on a trail designated for nonmotorized traffic, that a municipality, local authority or state agency has jurisdiction over, if such trail has a natural surface tread made by clearing and grading the soil and no surfacing materials have been added; provided, however, that a municipality, local authority or state agency after public notice and a public hearing may adopt ordinances or regulations permitting or otherwise regulating the use of electric bicycles on such a trail within its jurisdiction, including, but not limited to, the imposition of speed limits.”

The rebates are described on line 586–591:

“not less than $1,000,000 shall be expended for the department of energy resources for a fund to establish new rebates up to $500 for general consumers and up to $750 for low-income and moderate-income consumers and not more than 40 percent of retail price for the purchase of new and used electric bicycles; provided further, that the department of energy resources shall evaluate offering electric bicycle rebates at the point of sale through Massachusetts owned and operated bicycle retailers; ”