I'm sorry but your trying to associate bloodnoks signalling with US railroad practices which is completely wrong .
The A part of the signal description refers to the amount of aspects that the signal is capable of showing 2A = 2 aspect 3A = 3 aspect 4A= 4 aspect
The T section of the description refers to the signal being used in a "Terminating" situation i.e the signal is used before a terminating road or line , such as the last signal before enter a terminus station with the next signal encountered being a buffer stop (which should be lit with a red light facing an approaching train)
These terminating signals do not show a green light to a driver and act as a warning to a driver that he should proceed under caution.
They are set up however to use the scripting for the feathers and theatre indicators and DO work correctly when the scripted boards are placed in front of them.
There are no UK signals capable of permissive working in Trainz (at this time) . Each signal works as a stop signal and therefore will not allow the AI to pass it to enter a occupied section in front of it .
The only colour light that doesn't act as a stop signal is the 2 aspect distant (2AD) which is used as a way of illustrating to a driver as to either which aspect the next stop signal is showing (on track circuit block lines) or whether the route is clear through the next block section (On absolute block lines) or an intermediate block Home signal (on absolute block lines) .
As a read up on UK signalling practices I recommend downloading the current UK Rail group standards Rule books
http://www.rgsonline.co.uk/Rule_Book/Forms/Live_Documents.aspx?RootFolder=/Rule_Book/Rule Book Modules&FolderCTID=0x01200060B274261602B94B84F5B3E1E95DE5C8
Sections S , T and TS