More likely it was written by some cheap interns and requires getting unique ticket id from server for "controlling" purposes. Then there is one part time employee (met him, small talked a little) who goes from car to car with terminal and checks if those tickets are valid. I have some experience with gprs systems here, so probable flow:
- press button
- gprs roundtrip about button press with "no payment, free ticket" (2s)
- machine shows "printing ticket", asks server what to print (aka the idiotic unnecessary step)
- gprs roundtrip (2s)
- printer warmup? (?s)
- prints ticket
> to save power (and possibly SIM cost)
Nope, costs per sim are monthly per card, until you hit the data limit, then per MB. Those machines typically have enough power to keep connection alive.