Most of those people are not working on the Pipeline. The majority are on the North Slope production fields and in Anchorage.
The total Alyeska (company running the pipeline) employees ~800 people direct and ~1,000 contractors including those from ARSC. I and a few of my past employees have been one of those contractors.
Good thought about the comparison. Alaska is a harsher environment and the above ground portions (most of it) takes more maintenance than a buried pipe. Still it gives a reasonable basis.
Some thoughts about a comparison of Trans-Alaska Pipeline (Alyeska) compared to the Keystone XL.
Alyeska -> US portion of Keystone XL.
800 miles -> 851 miles
Pump Stations:
11 built (6 normally used) -> 18 planned
Pump Station Crew size:
6 ~ 25 -> ???
Total people employed:
800 direct + 1,000 contractors -> 50
Alaska is a harsher environment and the above ground portions (most of it) takes more maintenance than a buried pipe.