I think in most situations, it can be instantaneous.
On the Thomson Spirit 1, you can xfer at certain fixed (w/a fixed pulldown)speeds like 6,12,18,24,30 & max to 48 in NTSC.
And Vari-speed from 2 to 57 fps.
I think you should break it down like this.
Find out what telecine you are using. Each has its limits.
But then figure out what you are recording to.If its Ntsc, then really consider xferring it at 30 and leaving speed changes to the editorial session where they have more flexibility.
Xferring at 24 is obvious for sound sync issues. But if creating effects in post they will probably cine-compress anyway and remove the 3:2.
By also x-ferring 30 the time code can be locked and you can not lose any film frames due to frame dropping.