Just to expand on timelapse's excellent post...
If you're on a DVR or MID from 27L, we'll transfer you as soon as we see you turn (visually), or a few radar sweeps of you turning.
All ATCOs work under the premise that getting rid of you ASAP is A Very Good Thing. However, we need to ensure, if you're a BPK or WOB off 27L that we have a chance to get some separation from a 27R missed approach.
Occasionally, the timing works out that just as you turn towards BUR, the next a/c to land on 27R has just touched down, and the next one is therefore more than 2 miles out....so we can chuck you over straight away.
However, if the next to land on 27R is at 1 mile, or less, for example, we either keep you on frequency until you are well clear (suitable for slow climbing heavies), or we'll verify Mode C and get rid of you once you leave two thousand (i.e. through 2,400ft - more suitable for mediums).
Sometimes there might be low-level traffic on or off the lanes where a Mode C verification would be sought - usually either Police or Air Ambulance helicopters off-route.