in US, the restrictions vary.
It depends on the sections, loads, locos, type of wagons.
as per Simulators, which are based on real time data, the max speed achieved there was 60 mph. the restricted limit in steep ghats, descending down varies from 45 mph to 60 mph. 60 mph is quite rare, but in ascending, max is 60 mph to 65 mph.
in...
more... the movie, the certain parts were under supervision which differs than reality, u too know that. max the CWWR 777 touched 71 mph. :-)