Also, it's all well and good having iPhone and Android apps, but what about the rarer smart phone types: Windows Phone and BlackBerry (both 7 and 10) to name but two?
BlackBerry 10 phones can load some android apps but it's variable.
This is indeed a problem, and one I raised recently when our council decided to promote m-tickets for an app only on iOS and Android. Therefore, some tickets aren't available to Joe Public unless they change platform, or indeed buy a smartphone if they don't have one at all.
I assume that ATOC will still provide normal plastic cards, whereas some bus tickets are ONLY available if you use the app (which also means you need a debit/credit card).
I have no idea how much of a future Windows Phone (or Windows 10 for Mobile) has given its complete failure to gain traction over the years, and Microsoft clearly deciding its future is to release apps for all key platforms, thus making it relatively easy to ditch it one day if it decides to throw in the towel.
And BlackBerry is imminently releasing its first Android device, the Priv, which may well be the device to 'save' the company, and ultimately solves the issue of lack of apps by letting BB concentrate on security, the Hub and its own apps, while letting Google take care of the apps and content side.
As for other platforms, Firefox OS, Sailfish, Tizen etc - I think we can forget about any support there too.