CSX routinely shuts down Amtrak trains 448/449 for about a month each year. At least, that's what they've done every year for the past 10 years or so. According to the Amtrak service alerts, July 21 will be the end of it.
For the last couple of years, though, it's been MBTA doing track work between Framingham and Worcester. MBTA was busy at it about a month ago when I rode BOS-SPG on #449. What I saw looked like routine tie replacement...about every 3rd one or so, on the double track BOS-WOR segment, that they own.
So why do they cancel Amtrak when the MBTA schedule to WOR is unchanged and there is no service announcement regarding that line on their site? I'm guessing that MBTA is simply taking up where CSX left off several years ago with mostly 'ditch work' (personal observation from multiple trains back then) in screwing Amtrak every chance they get. While #449 was held for about 10 minutes due to single tracking about 5 miles east of Worcester (MBTA has a scheduled departure at that time), that's all the time we lost on that trip arriving in SPG about 10 minutes down.
What upsets me is that both CSX and NS have a habit of annual maintenance windows that shuts down the 1/day Amtrak trains but yet their own freight business is unaffected. To me, that clearly shows their anti-Amtrak bias.