That would be a technology challenge as well as OLT Express Poland has chosen to operate like a LCC using Airkiosk as a passenger services system while OLT Express Germany essentially still acts like a traditional regional carrier also using a legacy PSS
from Lufthansa System/Amadeus. While a free flow codeshare from OL
to O2 would be easier, doing the same the other way around would require Airkiosk to be able to fully support marketing codeshares, bilateral IATA interline e-ticketing etc. They should be able to implement either some sort of a blocked space codeshare agreement or at least integrate their websites to refer to each other especially given the large amount of routes to Germany planned by O2.
: I am still amazed how the media in Germany does not seem to question where the financing for this all comes from.