Andrea - I believe the BFHI guidelines for prem babies' readiness to begin
breastfeeding are well babies over 33 weeks and/or weighing 1300g - 1600g.
In the hospitals here which have not yet been through the BFHI process the
paed seems to assess each baby individually and then suggests that baby
should start breastfeeding.  Mom is encouraged to teach the baby at that
point, but there is often a change-over period when the baby is expected to
be topped up via naso-gastric tube or cup and spoon, and they are usually
test-weighed once there are some signs of intake to determine how much the
supplements should be.  Some babies, even the very small ones, learn to
breastfeed in a couple of days, some take several weeks.

Pamela Morrison IBCLC, Zimbabwe