I found the overhead picture of Sofia's airport to be of interest. My initial impression was "well, it is as wide as a runway ... easy mistake to make ... "
This post a bit further down by one of the commenters there cleared up some of my confusion.
Absolutely correct. Before the airport expansion completed in 2007, the Taxiway H used to be the runway. After building the new runway 09, it became the taxiway. However, up to now there have been no accidents of this kind for the last 5 years or so and Sofia Airport sees quite a lot of aircraft daily
What crossed my mind is the question of how often this crew had been to Sofia, and what went on during the pre-flight and pre-taxing crew briefings, what NAV/Chart data they had to hand, etcetera. I envision a less than joyful "tea and biscuits" session on return to home base.
On a more positive note, the alert controller caught them in time to avert anything worse than a red face or two.
Well done.
EDIT: looks like firefly bob got ahead of me in the kudos department.