In message , at 10:25:57 on
Fri, 5 Jun 2015, e27002 aurora remarked:
The only branch that is truly self-contained is the South-eastern one
to Abbey Wood. The North-eastern branch will be shared with trains
from Liverpool Street, and some freight.

My understanding is that Crossrail will have exclusive use of one of the
pairs of tracks to Shenfield, and everything else will use the other
pair. This is, of course, one of the reasons it's only going as far as
Shenfield, rather than Chelmsford (which would be a more logical place
in terms of passenger flow if the infrastructure had existed).
--
Roland Perry