Ruko is owned by the ASSA ABLOY group. hence ASSA has resellers world wide you should be albe to get Ruko locks everywhere. why ruko locks are not that common outside scandinavia might be because assa abloy just have'nt tried that hard to market them in other countries. the assa abloy group have lots other locks in their own product range and may not need any ruko locks to supplement their product range they market world wide.
I've had a bit of a dealing with Ruko AKA ASSA. In short they tend to be more secure than your normal lock mainly due to restrictred keyways and Patented blanks which make them hard to come by. A lot of factories using Ruko locks have a master key system which is usually designed by a reputable licensed dealer. One I have dealt with for the Army is the ???????. The Army needed spare keys cut and after searching around I found a method of locating who held the master records and via this I got spare keys cut from code. Sorry I can't give too much detail about the exact method as it is more suited to the restricted site.