We check the R/T of our ATCOs at least once a year with R/T sampling. This is seperate from yearly competancy checks when R/T is monitored as part of an ATCOs overall performance. Then as a watch LCE, I will talk to watch members throughout the year if I feel their R/T in a particular situation is sub/non standard.
Thankfully, I've got a good watch who know their onions.
On the R/T sampling form, there is a section where I can critique the R/T performance of a pilot/airline if I feel I need to. This is then fed back from our unit management to the airline base captains or flying training organisations.