Various Brussels public transport tickets allow access to the SNCB network in the Bruxelles-Capitale region. By looking at the map provided by STIB, there are many SNCB lines and stations covered. How do I find out practical details for this network, such as timetables, frequencies, lines, and so on? I am only interested in the part inside the Bruxelles-Capitale region, since that is covered by the same tickets used with the local public transport. I could not find this information on the SNCB website.
On the map page of the STIB that you mention, you just have to click on "Consultez le plan dynamique" to open the dynamic map. Trains are the dash white and blue lines. Stations have a logo with a white train on a blue background.
In practice you don't have to bother about this. Whenever the train is an option, the STIB journey planner will show it and provide the details.
You should also note that at the time being, train plays a minor role for legs within Brussels.
You can also have a look at the network map if the Belgian Railways (SNCB/NMBS):
The SNCB also provides pdf timetables by line:
Have a look at the following lines: 25, 26, 28, 36, 50, 60, 94, 124 and 161