Aussie Andy,
Is the "2000' nth bound / 2500' sth bound" stuff promulgated officially, or just "local practice"?
Nope, not official & I've not aware that it's local practice. Just a suggestion by a member as a possible help to seperation. As long as you stay above the minimum and below the CLL, you can use any level you want.
As a newcomer to the BK area , I tend to make a number of calls during the lane transition. The freq hasn't been busy on the occasions I experienced and as there is a lot of traffic, I will continue to make calls.
I agree that a seperate freq like R405/Victor 1 would be of help.
Having experienced one aircraft on the reciprocal not making calls compared to others making calls, I know which is safer and to me more preferable (yes, I did see & avoid + make a call to advise the other pilot my intended action ( head on = turn to right), got a mumbled "Oh yeah" in reply).
Bk can be very, very busy. The lanes + GA reporting points all act as magnets for aircraft and the mix of types means see & avoid may not happen as we all hope (personally, hearing where and what an aircraft is up to works a lot better for my situational awareness).