Very close
Railroads have been using run through power for over 75 years, the practice dates back to the steam era, although it was very rare back then. It really took off during the diesel era.
Locomotives are accounted for based on horsepower hours (hphrs), not just hours. The locomotive's horsepower is multiplied by the number of hours it is on the other road. A 4000 hp engine accrues more hphrs than a 3000 hp engine. For a modern railroad, they deal in tens or hundreds of millions of horsepower hours per month.
Run through power can be used on many types of train, actually it has been used on pretty much every type except locals and switchers. Manifest, perishable, auto, intermodal, bulk and passenger trains have all operated with run through power.
At the end of the month the railroads compare records and agree on how many hphrs they owe each other. If there is a large imbalance they will try to make up the deficit. The imbalance can be caused by one road having more miles/time on its portion of the run through operation, or by one railroad having to use its engines only due to some operational issue on a portion of the route. For example on UP coal trains, the UP engines were used on other roads because a UP engine had to be a leader on the areas where the UP had cab signals. In the early days of DPU, other roads wouldn't have compatible DPU so UP engines had to be front and back on the trains to use DPU.
The ways they will pay back the horsepower hours is by increasing the number of deficit railroad engines in the run through power mix (either in that service or another run through service) or by giving the owed road engines to keep for a period of time to "pay back" the hphrs. If railroad A owes railroad B 20 million hphrs, they will give railroad B six 4000 hp engines to use for 31 days (6 eng x 4000 hp x 31 days x 24 hrs = 17 million hphrs). Those engines will be used in regular freight service on railroad B and could show up on any train except a run through back to railroad A.
In the video, the single UP engine on the manifest train wasn't necessarily cut off a unit train, it could have come over on a manifest train or could have been a hphrs payback engine too.
In recent years, with PSR, railroads have cut back on run through manifest and intermodal trains, not because of the power, but because the railroads decided to stop switching blocks for other railroads.
It was extremely rare for horsepower hours to be paid back in cash. Railroads would go to great lengths to avoid having to do that. Pretty much, the only time that happens is when the railroad owing doesn't have engines (or engines the owed railroad wants to use) to pay back the horsepower hours. For example, a shortline or regional that only has GP engines wouldn't be hard pressed to pay back hphrs with GP38's.
Back in the 1970's the NdeM became highly indebted to the MP for hphrs so they paid the MP back in gondolas. The MP was buying gons made at a plant in Mexico, so the NdeM tacked on a run to pay back the hphrs. If you ever see a picture of a black MP mill gon with white lettering and grab irons, that's one of the payback gons.
Many times on shortlines, particularly those that were spun off a class one railroad, the service agreement between the class one and the shortline allows the shortline to use the class one's engines for a period of time without accruing hphrs. If a shortline serves a grain elevator and it takes 30 hours to get a unit train from the interchange to the elevator, loaded and back to the interchange, the class 1 might give the shortline 48 hours "free" use of the engines to use on the grain train, so no hphrs accrue unless the shortline or the elevator does something outside the scope of the agreement.
There is also a fuel adjustment on the run through power where railroads pay each other for the difference in fuel between delivery and receipt of the engine. Railroad A gives railroad B an engine with 2500 gals in the tank. If railroad B give it back with 1500 gals, then railroad B owes railroad A for 1000 gals of fuel, if railroad B gives it back with 3500 gals then railroad A owes railroad B for 1000 gals. The fuel readings can be done by the engineers and reported on their timeslips or in the modern world, the AEI readers can get a fuel reading automatically. There are also standing agreements on fuel usage, particularly on runs where the engines aren't fueled. The trip over railroad B on a unit train move takes an average of 2000 gals, so ther is a flat charge of 2000 gals for every engine on those unit trains (that make the round trip on those trains).
