Taking a bicycle in the bus in Macedonia is an easy thing. There are no extra fees. But, under the condition that the bus is a regular bus, and there are not a lot of passengers. It is mainly the issue of space where to place the bicycle. Some connections do not have regular, big buses, but mini buses that do not have any luggage space. It is best to ask the driver if this is possible, since the drivers are the bosses of their buses. And only then get a ticket for that particular bus, because one needs a different ticket for a different bus company.
It is a general rule of thumb that Sundays all the buses going towards Skopje are full of passenger. While on Friday evenings, or even Saturday mornings all the buses that leave Skopje are full. This means that if one wants to take the bicycle in the bus, may run into a problem on these days.
When taking the bus it may be nice to use some cardboard as wrapping, because the bike may be scratched, a lot. However it is not necessary to do anything special.