rcapiloto,
Then you well know that on the S58T there is a mechanical stop, ground idle before you advance it through the mechanical detent when it becomes the flight idle stop. The Bell 412 EP doesn't have the same engines (though the 412 does) and all the 412s as with the 212 have an electrically activated idle stop release, so the systems are not quite the same. It's a shame Bell never adopted the Sikorsky system.
WBS,
As has been mentioned, the best angle of climb speed for any helicopter is 0 knots groundspeed, i.e., a vertical climb. However, in most cases this is not practicable as much of the time you will not have the power reserve to achieve it. In most twin engine helicopters, when they are being operated to performance class one limitations, the 2 speeds which are relevant are the best rate of climb speed which, as you say, is 70 knots for the Bell 412 and the take off safety speed, which for the Bell 412 is 45 knots. This is only relevant during the initial phase of the take off and is basically the speed at which the aircraft will maintain a rate of climb of 100 feet per minute and remain clear of obstructions by the prescribed amount in the event of a single engine failure after TDP up to 200 feet. At this point, the aircraft is accelerated to Vy for the remainder of the climb. Depending on which RFM you're using (FAA/JAA/UK) it's in the Category A or Class 1 supplement.