This type setup here is referred to as a 'mat job'. Yes, it is 'old' technology, and is slowly going away. Three or six pots was standard before pad mount units. 250, 333, 500 KVA were common, occasionally 750s.
Today, when there is a failure in an existing mat, the failed pot will be replaced, or the full set may be replaced.
AS to the building in the pic, yes it is vacant, as the avionics co that was there outgrew to 65k SF.
As to the vegatation, sorry to say it is 'common' with mat jobs. The transformers, primary pole and wiring are POCO owned and maintained. The fence is locked with a POCO lock. The POCO does provide forestry work, but most of the time it is done after a failure, blown cut-out, etc.
Guess this is not something you see on the west coast??