Can ICAO airline designators be reassigned to a new airline? Is it possible for three-letter ICAO airline designators to get reassigned?

In particular, I'm trying to find out if BKL was previously used for Baikal Airlines (ceased to exist in 2001) and reassigned to Barkol Airlines (founded 1996, although it's unclear when they received their ICAO code).
Yes. As per rules ICAO can reassign the three letter airline designators after a period of 60 days. 


  When a designator is no longer required, ICAO should be informed immediately. Any such designator so released will not be reassigned until a period of at least 60 days has elapsed. 


The designator BKL was used by Baikal Airlines and is currently used by Aircompany Barcol.

Another example is the airline designator WOW, which was used by Air Southwest  and is currently used by WOW air.