AF,
Not sure there is a direct/complete answer to your question. In the UK there have been one or two trials: one in London and one for Somerset/Avon that I am aware of.
Following the trial, LFB did not pursue any helicopter support. Not quite sure about Somerset/Avon: their trial was recently completed. I heard a rumour that this might be followed by a further 12 month trial.
There is some use of heles in UK forest fires, but much less than other parts of the world. I think they are mainly contracted by the forest owners (e.g. the Forestry Commission)
From time to time a Fire Service makes use of police heles: usually (in my experience) limited to things like FLIR downlink which can be fascinating (although I don't know how valuable).
Is there a track record in other parts?