As far DUS, TXL/BBI and Germany in general are concerned, I do think Air Berlin brings OW airlines and passengers several big advantages:
- Better OW corporate products and sales/after-sales presence regarding corporate customers
- Of course other OW products such as RTW tickets get more interesting especially ex-Germany
- Better presence at German airports, from being able to check-in early to handling irregularities. This has been a major irritation so far, IMHO.
- Better ability to offer alternative OW connections in case of irregularities ex-Germany
etc.etc.