B&M/PAR Milepost Question

I'm not sure if this question properly belongs here, or in the current operations/Pan Am forum, but here goes:

The route followed by today's Freight Main Line jumps between multiple historic rights-of-way that were originally used by multiple B&M predecessors. These include (among others) the Stony Brook Railroad, the Fitchburg Railroad, the Vermont & Massachusetts, the Southern Vermont, the Boston, Hoosac Tunnel, & Western, etc. In most cases, each time the route shifts from one predecessor ROW to another, there's either a short or long mile since the original milepost locations weren't changed, but were simply renumbered based on the new origin point. I've been able to figure out the sources of most of these long/short miles (either a predecessor route change or a line relocation) based on the valuation maps, but there are a few that are a puzzle, and I'm hoping someone with more historic knowledge of the B&M can help fill in the gaps.

Specifically, I'm looking for the reason the distances between (current) MP 364, 365, 366, and 367 are (based on measurements along the tracks) are 7022' (364-365), 3379' (365-366), and 5438' (366-367). While those may average out to 5280', the milepost locations as shown on the valuation maps are definitely not anywhere close to 5280' apart...

Thanks.

There was the Birch Hill Dam mainline relocation in 1940. Royalston.

Where I'm looking is about 10 miles further west, in Orange.

Mebbe this clears up or causes more confusion, but a comparison between ETTs 10 (eff. Nov. 22, 1931) and 36 (eff. Nov. 14, 1941) shows mileages .01 or .02 less in 1941, 64.66 v. 64.65 for Gardner and 70.53 v. 70.51 for Baldwinville as examples. Royalston -- west end of the Birch Hill Dam relocation -- shows as 75.58 v. 75.33, reflecting the shorter routing. The .01 or .02 differences continue west. The difference at Johnsonville is more -- 174.12 v. 173.79, hinting at a relocation from possible Hoosic River or tributary flooding. Given the financial pressures of The Depression and the boiler-plate nature of ETT typesetting, it's strange that differences of .01 or .02 were measured, let alone documented.
As far as Orange, the 1941 mileage is 86.00. If the later mileage of 366.4 in both PAR ETT No. 3 (eff. June 15, 2014) and New England Railfan Timetable Guilford Rail System Timetable #1, {eff. Dec. 1, 2002) gets the -280 treatment, that comes out to 86.4, .4 miles west of the older location and west of the Water Street XNG. Guessing that relocation mighta been made as a convenient recrew/tie-down point for EBs.
The resolutions to these and so many other puzzlements are possibly in the B&MRRHS archives.

Interesting. The Orange depot is shown on the 1915 track chart I have as just east of Water St, at roughly 86.35. It's in the same place (without the depot buildings) on the 1980 track chart as well. 86.30 is shown in the 1911 ETT; 86.02 is listed in 1957. What we don't know is if the "miles from Boston" in the timetable is actual measured distance or if it's based on the number of mileposts (not the same thing, clearly). Most railroads tend not to remeasure and move mileposts, but use short or long miles instead. Clearly the B&M had a different practice, at least for a while.

I don't get the total upshot of the post. Did B&M relocate mileposts to allow for the line relocations? I know personally about the renumbering of mileposts for the Freight Mainline out on the west end and D&H. A good example is at Crescent. On the joint line between Crescent and Mechanicville, both railroads had their own mileposts. There is presently a short mile between MP 477-478. Gilford used the B&M milepost locations and repainted them for the mileage from Mattawamkeag, vs. the old mileage from Boston. At this location, Guilford simply just painted the next physical milepost for the consecutive number. The 477 milepost was a B&M milepost. Their mileages continued out what is now the Rotterdam Branch. The milepost at 478 is from the D&H series, so the location is not actually 5280' from the last milepost, on the former B&M series.

No, the B&M didn't move mileposts (as far as I can tell) when a line relocation happened.

The starting point of the question was the fact that the milepost locations in Orange between MP 364-367 vary considerably from being anything close to 5280' apart (7022' for the first mile, 3379' for the second mile, and 5438' for the third mile). I can't find any evidence on the valuation maps of the line having been moved from where it was originally laid out, and I'm trying to find out if anyone knows the reason for the odd milepost spacing.