The 1.2 miles in Framingham were paved in 2015. Construction of a 12-foot-wide multi-use path along the remaining 2.4 miles in Natick is being proposed. That includes a grade separated crossing at Route 30, as well as replacement of the CSX bridge over Route 9.
Update 8/1/2018: Natick is now at the 100% design point and will be put out to bid in late 2018. Construction is expected to start in 2019.