I was thinking that, depending on how exactly the Presto card works, it might simply require a bit of programming in the turnstiles for programmed trips.
They might not be able to easily get in the equipment to buy tickets or charge a set fare, but I would've thought that if someone wanted to buy a metropass on their Presto card, it would just have taken a bit of programming in the entire system. As long as they use the same technology (which I assume they do,) wouldn't they just have to add the turnstiles to whatever presto network there is?
Nope, totally different technologies. You can no more get a Presto card to work with a normal TTC turnstile than you can get a key to open a combination lock.
My understanding is every single Metropass for a given month has the exact same "password" (for lack of a better term) invisibly "printed" on its magnetic strip. You run the strip through the slot on the top of the turnstile, the machine performs a really simple "is this my current password setting or not" check, and you're in or out. There's nothing special on the card that links it to you, and no opportunity to write or re-write data to it. All the magnetic strip really does is (a) give the machine an easy way to read the card and (b) makes it moderately difficult to conterfeit them. Likewise, the turnstile is "dumb"... it can't think and process on its own, and isn't constantly talking and checking in with a computer network.**
Presto works by RFID technology and is a totally different beast (I haven't seen the back of one of the cards, but as far as I know, there isn't even a magnetic strip on them). Embedded in the actual plastic structure of the card is a metal antenna which can remotely transmit data at distances up to a few inches. Not only do the radio waves allow information to be transmitted to the card, but the card is also able to convert radio energy into a small amount of electricity, so when you wave the card near the reader it can (briefly) power up an onboard microchip with writable memory and "think"--this allows them to not need to squeeze a battery somewhere into the card. Your card "knows" how much money you have stored on it, and "talks" to the turnstile either to figure out how much money it should wipe from your balance after you go through or to persuade it that you're a legit owner of a valid monthly pass and you should go through.
If RFID readers were installed on TTC turnstiles then yes, it would be a matter of tapping in a few lines of code somewhere to make it so that you could, for lack of a better term, put a Metropass "inside" your Presto card. You'd wave the card, it would strike up a chat with the turnstile, and the two would agree that because it's month X, you're allowed through. It would improve on the current Metropass by being contactless and considerably less susceptible to counterfeiting. They'd also be able to offer new pricing structures--for instance, a setup is possible where you pay as you go at the same price as tokens until you've spent a monthly pass's worth, at which point all subsequent travel is free for that month.
The hangup is that the TTC has indicated it will only install RFID readers in its turnstiles and on its surface fleet if someone else wants to pay for it. This is in stark contrast to the rest of the GTHA transit systems--which, to be fair, have fewer vehicles to outfit and less already invested in fare collection infrastructure. Rationalizations aside, this is generally in keeping with the TTC's attitude of rigorous indifference towards riders originating outside its system.
I haven't ever heard a figure quoted for the per-unit cost of RFID readers, but seeing as MasterCard can get them into every Tim Horton's, I'd wager they must be considerably cheaper than they were even three years ago.
Most of us expect that at some point either Metrolinx will cave and fully or partially fund Presto's rollout across the TTC, or it will twist the TTC's arm into installing them by blocking financing for something else until they comply. One thing that ought to be interesting is watching what sort of fare collection is supported on the first Transit City lines, because Metrolinx will hold be the notional owner and have a degree of operational shot-calling power.
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(I may in fact be oversimplifying... there could, for instance, be separate identifiers for adult metropasses versus the discounted ones that get logged by the turnstiles for statistical purposes, and rather than a monthly code that needs to be changed, the turnstiles might have an automatic internal calendar that checks against a date written into the card's strip, which would presumably cut down on the amount of physical fiddling with them. AFAIK the TTC doesn't ever really talk about the precise functionality of this stuff, for obviousish reasons.)
