I know ACSES isn't active, but I believe an ACSES signal unit can still pick up more signal aspects than the standard unit, even in MNRR territory. A standard cab signal unit can only display four aspects (Clear, Approach Medium, Approach, Restricting) whereas the ACSES unit can pick up things like Cab Speed, Approach Limited, etc.
But MNRR does not have those additional aspects. For getting the additional aspects you have to have the second pulse code carrier frequency, which MNRR is in the process of installing, and it is not critical for MNRR because most of the additional aspects are for speeds above 80mph.
The original cab signaling system had the basic 4 aspects on a single carrier frequency. Even if a train is equipped with ACSES unit, it cannot get the additional aspects from a piece of track that does not have the second carrier frequency, and it simply falls back to the original aspects.
There is no cab aspect for approach limited in the old or the upgraded ACSES system. The only cab aspects are:
150 mph Clear (Requires second carrier frequency. Legacy Units get Clear 125 mph)
125 mph Clear Original PRR System Code (originally in PRR it meant nominally 80mph)
100 mph Clear Used for high density signaling (Requires second carrier frequency, legacy units don't receive this)
80 mph Cab Speed Used for most high speed turnouts. (Requires second carrier frequency, legacy Units get Approach Medium 45mph)
60 mph Cab Speed Used for high density signaling. Compatible with LIRR ASC System (Amtrak legacy units couldn't get this even though it is on the old carrier frequency)
45 mph Approach Medium Original PRR System Code
30 mph Approach Original PRR System Code
20 mph Restricting
0 mph ACSES only, not available in cab signal
For a turnout you will get a Cab Speed with the appropriate speed for the diverging track