It doesn't seem to work (latest version 5.13). I am absolutely positive that many of my airports have airline codes assigned in the .bgl, I even double checked in the sim (e.g. FlyTampa KBOS or Aerosofts EDDB). Still none of these airline codes get read by MakeRwys, the g5.csv has no airline assignments at all, nowhere. Can you check if it works for you?
EDIT: And just for context - the rest of the data gets read correctly, taxiways, runways, gates etc. Here's a snippet of what the runway.txt says for KBOS, as you can see Airlines is empty, even though it's clearly assigned in the .bgl:
Gate A9 [#G35]: N42:21:48.0075 W071:01:16.3371
Type 9 (Medium Gate), Size 20.0m, Hdg 16.8T
Airlines:
Gate A10 [#G36]: N42:21:48.3314 W071:01:14.6829
Type 8 (Small Gate), Size 15.1m, Hdg 3.7T
Airlines:
Gate A11 [#G37]: N42:21:49.7892 W071:01:13.2698
Type 8 (Small Gate), Size 15.1m, Hdg 306.2T
Airlines: