I am betting that they didnt bother trying to sell some of that stuff. I am amazed at some of the junk they left. That entire scenic set took alot of work and to just leave it behind, I have to think they didnt bother looking for people to grab that stuff or it would have been gone alot more quickly or gone period.
I wish I had a chance to grab something like that. I really do hope you have a nice place to put it.
And as mentioned above, dont cut the tracks! They will just slide apart easy if you separate them from the surface they are on.
I actually have a HO scale train set myself. Not currently assembled though, but do have some very nice engines for it.
As for the amount of work, hundreds of hours if I had to guess but could be more based on technique used. You set your base out, you carve up the foam and mold any plaster, base coat the foam/plaster, possibly put a base layer of flock/sand/gravel down but definitly paint, put other layers down, various addtions like trees after that, put gravel, put your final coatings to make things stick etc etc, all done by hand. Just to give an idea of the sort of work that can go into this sort of thing. And you have to take into account the amount of time it takes paint and glue and such to dry - tack that on to the time required if you have several people working at once.