There are 2 sets of tracks in Lancaster. The CSX Fitchburg Secondary runs through Clinton and as far as Leominster. It has been a small-volume daylight operation, but recently added a new recycling customer in Leominster. The PAR Worcester Main Line also runs through Clinton and the more easterly section of Lancaster into Ayer. This line is much more active and has been running sometimes more than 100 cars at night and sometimes more than 100 in the other direction during early predawn hours. For the near-term future, there may be additional trains on the Worcester Main Line.
The times are approximate and not set in stone.
There's more information, but it may be excessive for your needs.
Happy hunting!
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