I think you are right. From the website:
"Officers are authorized to enforce GO Transit by-laws, which govern passenger conduct, fare inspection, and use of our facilities. To ensure you have a safe ride, officers are authorized to enforce the following statutes: The Criminal Code, Controlled Drugs and Substances Act, Youth Criminal Justice Act, Trespass to Property Act, Liquor License Act, Sections 17, 28, 33 of the Mental Health Act, and Safe Streets Act."
I suspect a couple of things:
- since it says they are "authorized" to enforce various statutes, they are likely appointed as Special Constables under the Police Services Act or whatever it is called now.
- if they are S/Cs, their appointment likely includes the phrase "on or in relation to" (Corporation property).
The only HTA authority they have is to demand (and you must produce) a driver's licence or identification when enforcing ML bylaws on Corporation property.
As for directing traffic, good on them for taking the initiative.