Fortunatelly yes, it is, just place the files accordingly and should run just fine. Or if you experience problems with the overlapping sectors, place the Promods def file below the Project Balkans primary files.
Not sure exactly what has fundamentally changed the course of the game since its newest update but Project Balkans lost the compatibility with Southern Region map addon, this issue was also explained by grega and his team once before.
Since the overlapping affects only small areas around LJ, MB in Slovenia and ZG, RI in Croatia, those warnings in the log file are expected, but O.K.
One thing to note, when running in conjunction with Rusmap, Promods and Scandinavian Promods Addon by ChrisNOR94, it sometimes crashes the game to desktop. Maybe grega and his team should look into this as well. So far when adding Paris Rebuild 2.1 by Grimes affects the stability of the whole game and crashes it, so that is a no, at least for now, pure Promods with that addon and a select bunch of them others, should still work as intended, but that's beside this topic.
Confirmed that when selecting the trucking company HQ as Maribor resulted in CTD, will try also to run as Ljubljana as the primary city for the HQ.
Maybe this is just a bigger mod conflict, will test it again to confirm for sure.
Update : only selecting Maribor as the HQ crashes the game to desktop, Ljubljana is fine, also think that the before mentioned Croatian cities should be fine.
Using a test profile I can investigate further this issue co-running with Rusmap, Scandinavian Addon and Promods with Project Balkans. For now only Maribor didn't pass my test, but I'm sure that removing a stranger mod should re-stabilize the game again.
Solved removing a stray invisible wall remover, now all is well.
Best regards and happy trucking.
. Will the ferries be the only way how to reach Albania or will you make also a connection whit FYROM through Ohrid?