Mark,
Check out the install at page 24.
https://ogrforum.com/topic/gre...hern-railway?page=24
it continues on 25, etc.
https://ogrforum.com/topic/gre...hern-railway?page=25
JMRI software is used along with RR-cirkits.
Since the software is 'external' to what ever type of system is used to power the railroad, it can be incorporated into any size/style railroad.
It cost me about $2,500 to install including the PC and that was almost 6 years ago.
I got 'good prices' on the signals (about 5 bucks each) so the price can rise quickly if you need a lot of signals as signals can cost upwards of 25-75 dollars each.