Hi. sure there are busses from several places. But we cant guess from where you want to enter the country

About domestic train travels:

http://www.zfbh.ba/

http://www.zrs-rs.com/

Io sono in Croazia, potrebbero esserci bus, ma sono inclusi?

Buses are not included, unless they're run by the railways. But that is not the case for the ones to Bosnia.

Daddy/uncle google will help in a few seconds with these questions. S-J does indeed have pretty good-due to lack of railways-connections to all surrounding major cities. BUT those from Beograd do NOT serve the city proper-due to those immense rifts between the various tribes there they end in the Serb quarter which has a different name (and I forgot which)

In fact this does not only apply to Bosnia, but also more or less to Serbije and Macedonia- NO-or very, very few-trains over borders to there. A  pass is a waste of money using there-the trains that do run-if at all-are pretty cheap-even cheaper as the worst of regionale in south -Italia