Looks like Rock Springs will be interesting.
Talking of US data there was a study done by NYU and published in Aviation Psychology and Applied Human Factors that looked at 4,755 helicopter accidents (all types of operations) from the NTSB database. The researchers compared the underlying causes and also the factors that differentiate daytime and nighttime helicopter accidents.
The number of fatal accidents occurring at night was reported as significantly higher than during the daytime. The combination of night flights and adverse weather conditions is shown to be particularly fatal in accidents.
If it is economics that drives the use of singles it is a pity that a well equipped IFR certified machine means a twin, irrespective of the pros and cons of engine number. I may have missed it here but oddly lack of weather data is also commonly raised as a reason to stay low and fly VFR.
The NTSB meeting on HEMS IIRC threw up many issues with the US HEMS business model. Yet it does feel that many are arguing for the status quo of special VFR, or at least NVIS assisted VFR, for purely economic reasons. Yet there are indications that HEMS is being used in the US for cases that in Canada, Europe, Australia etc would not justify a helicopter (the Maryland State Trooper accident for example), surely a waste of resource that if addressed would allow improvements in equipment, training etc.