Cool reverse engineering indeed! For those who want it easier, the Helsinki Region Transport Authority HSL offers the arrival time predictions through a service called "Omat lähdöt", which has an open API too. However, the textual messages are not available so that's new. As the post mentions, the predictions are based on the GPS locations sent by the busses, which are not available to third parties (unlike the locations of the metro, trams and trains). For more information about the HSL Developer Community and open data at HSL, see dev.hsl.fi.

I find it silly to complain about grammar in what is clearly a typo, but I'll comment since you seem to be interested in grammar.

I know there are grammars with various conceptualizations, but 'may' is typically considered a verb. Perhaps you were thinking of the month May, although usually people who speak English natively would expect it to be capitalized. Interestingly, many adjectives in Japanese can predicate a sentence without a verb.