This app was mentioned in 3 comments, with an average of 3.33 upvotes
Creo que hablan de esta https://play.google.com/store/apps/details?id=com.matungos.stm.mvd
Fuera de eso ¿Tanto te cuesta buscarlo ? La pregunta va en serio aunque quedó de medio hijo de puta que no quiere ayudar xd
Hello! the prices of bus tickets and such have been answered already so I'll adress the accessibility part and schedules.
If you have a smartphone I recommend downloading the STM app, its pretty intuitive but in it you can check bus timetables as well as routes and bus stops. You can also mark the places you want to go and it will recommend buses that go from the place you are now to there, and you can even follow most buses in the app via GPS.
Most services have not linear schedules, some work 24hs with more frecuency, some with less frecuency at night, some have services only during the day and stop around midnight, etc. You need to keep track of that beforehand so you don't end up someplace without a bus service at night for example.Here you can also check bus times individually (write the bus number where it says "Linea" and select the day you want to travel (for example "Hábiles" means Monday to Friday) and you can see the timetable for that bus and where it is expected to be in the most important intersections (you can google-map those) you should keep in mind though that bus can be late/earlier than where it says in the apps, so I'll recommend being at the bus stop around 10 minutes earlier for the bus you want to catch, and don't be surprised if it isn't there 10/15 minutes after the assignated schedule. The most reliable way to know when a bus will be coming is through checking the GPS service.
Bájate está app para los ómnibus! https://play.google.com/store/apps/details?id=com.matungos.stm.mvd