If late morning to early afternoon is an option, that might prove productive. There will be T activity, and there should be 23K and 205 activity -- mebbe. As far as POSE/SEPO and POED/EDPO, the variables are both infinite and confounding. There are also locals whose duties vary with the day. There may also be coal, limestone, oil, and grain moves in either direction. How big a traffic jam Ayer is generally is largely determined by connection and recrew issues both near and far. Freight activity is usually in the spaces between T activity, but sometimes an EB will stop just clear of the platform.
"A gray crossover is definitely not company transportation."