Stranger talk refers to (fragments of) conversations that people have with other people who they do not know. These conversations have no meaning other than to pass the time, be polite, or ease tension in a stressful situation. Stranger talk can best be described using examples:

Passing the time
This type of conversation usually occurs when groups of individuals are awaiting the arrival of something (bus, train, etc.) or the commencement of some event. During these times, the conversation is usually initiated with a question, such as:
1) When’s the train/bus/mono rail supposed to arrive?
2) What time do you have?
3) What the hell? Get the fucking opener off the stage and get the (band of choice) out here, eh? ("eh" is optional depending on Canadian citizenship).

Being Polite
The scene: you’re in line and someone is taking forever using the bank machine, but you don’t care: it’s the first day of your vacation and you’re in chill mode. The fat lady in front of you huffs and sighs a few times, then turns to you and says (something like) "can you believe this?"
You:
1) Holy shit, I know. HURRY THE FUCK UP!
2) Ya, what’s going on?
3) They should have more than one machine here.
But you don’t care. You’re just being polite.

Tension
These types of conversation are usually very short and contrived to allow the initiator to feel more secure in their position, usually by eliciting a positive answer from the other party. For example:
1) Hey man, I doubt the fire will reach this floor. What do you think?
2) The subway’s probably just stopped ‘cause of some jumper, eh?
3) It’s just a glitch. I’m sure the elevator will continue in just a sec.