The ticket reservation system of PKP PR (Polish regional railways) was the worst AJAX solution I've ever encountered on the Polish Internet. When I entered my data to buy a ticket, it notified me that my e-mail address had already been used, so I had to sign in to proceed. I had to do it in a separate form in the sidebar. Then it turned out that I had to use my login name, not my e-mail, which I didn't remember, since most websites can sign you in with your e-mail only. When I finally managed to sign in, the system had long discarded all the session data, and I had to type in my order again. In all three steps of the wizard, I couldn't send the forms with [Enter], I had to click a (very small) "Next" button which triggered the AJAX action. In the "Select payment method" section, they divided the list into three sections, each one of these comprising of a separate set of radio buttons, so even though I selected "Credit card", it redirected me to the website of a designated payment service provider.
I checked the page of the maker. In English, it says "IT-Trans sp. Z oo from its inception in 2010, specializes in the delivery of services and products for the market of public transport. We are a Polish leader in online train tickets. For created (sic) by the developers own system (what was created by whom again?), we can sell all train tickets, as well as public transport (you can sell public transport?)...A full range of IT-Trans uzupłeniają (że what proszę?) passenger information systems, fleet management, passenger counting and operator services." On their website, the only place to change the language is in the footer (?), and the locale is not preserved, either in the session or in the GET params—when you navigate to another section of the page, it switches back to default locale.
Next time there is a public order for a ticket system, I will place my bid and make my own solution in PHP3 and Joomla.