an initial mass-lock to occur regardless of whether it's an asteroid, adder or anaconda, and then you are released from mass-lock according to mass (maybe with a short time-delay).
There is an initial masslock (except from asteroids) which is released almost instantly (within 0.3s). This give a chance to change the flight path in time without full turnback, and also to stop far from pirates exactly as earlier.
I encountered an asteroid. I held my breath as I aimed my ship fairly close to it. My Torus shut down with a mass-lock warning. Shortly after passing the asteroid, the all-clear green light returned and away I went.
This safety brake feature check the angles between your heading and directions of asteroids in your scanner, and within a few degree trigger slowdown at about 10km to reach normal speed about 3km before the rock. This is not a persistent masslock so you will be in green alert soon again, but make sure you corrected your direction (or left behind the rock) before start Torus to avoid accidents.
I am getting mass locks from the GalCop station very early
Objects over an Anaconda cause masslock right at scanner range as usual.
it would be unpredictable when the mass-unlock happens?
Usually near the 20km sign on the scanner (4/5 of max. range), except non-rock stations, Anacondas and other [wiki]Bigships[/wiki] at scanner range.
does it take into account if more than one object mass-locks you?
No, the effect is not added up from different ships.
Increased MassLock distance
Nothing is increased, the maximum is still at scanner range.
when jumping/Torus'ing into a group of pirates
You still slow down instantly when your scanner detect a ship (as a safety feature), but you can hit the jump key again if you want.