I have neither seen a Pan Am speed bulletin or gone deliberately chasing a train on the Worcester Main (both "chase" and "main" being loose terms) in quite a while, but I'm going to guess from the last time I witnessed a train going across the Wachusett Reservoir causeway, the bulletin speed is already 10mph, even if it's allegedly 25 by my several years old timetable copy.
As a taxpayer of the Commonwealth as well as a resident of the Town of West Boylston, my humble opinion is if my tax dollars go in part to paying for track upgrades that allegedly "protect" my water supply by allowing safer track conditions, I'd much rather those trains utilize those improved track conditions and move right along safely on the properly maintained track through my town, rather than needlessly plodding along at 10mph and only causing an enormity of wasted time and fuel burn for both the trains and any motorists unlucky enough to encounter one at a crossing in town. Class IV I believe allows a 60mph freight speed; cutting that to 40 or 50 is plenty enough of a safety margin for me and the water tap I drink from in my kitchen, especially if the railroad is safeguarding the watershed by applying better funding, better equipment, better staffing, and a corporate desire to maintain the property at a given level at all times.
I would hope that CSX will very carefully scrutinize any proffered bag of money from the state and note the strings attached to it, and maybe just maybe say, nope, we'll take on this upgrade out of our own pocket and thus be able to use the federal preemption excuse and all else and run their trains at a speed in keeping with real and not perceived safety margins and per their operational objectives, if spending millions of dollars only to run at 10MPH on Class IV track is as ridiculous a concept to them as it is to me.