Just found this "diary" of a Celtic fan there for their trip a few years ago - the same one detailed in the article I posted earlier.
Despite the buses, he caught the metro to the ground without any issues. In fact it reads that he didn't even know about the buses until he came out the ground...
I know it was a different stadium, but Celtic seem to be the last British club to have played AEK and they were strongly advised to use the provided buses...
https://www.thescottishsun.co.uk/news/3067383/celtic-fans-bus-aek-athens-greece-free/