[tuukkah]

The ticket API and SDK for the greater Helsinki area subway, trains, trams and busses is here: https://sales-api.hsl.fi

There's a call for new service pilots: https://hsl.fi/idealab

The official open data and APIs including GTFS, GraphQL and MQTT here: https://hsl.fi/en/opendata

Disclaimer: I've worked on these at HSL.