Transit Times not being calculated in ASCP unconstrined plan

We are on 11.5.10 with APS on R12. We use consistantly item attribute (source org ) to control sourcing of all Internal Orders. What we have discovered recently that while the item attribute works fine with the ASCP plan in terms of determining sources it does not use the Shipping networks to read and offset transit times. Transit times are loaded correctly with default. We do not wish to migrate to Sourcing rules as a replacement for item attribute at this time. Is there any way to ensure that transit times are offsetwithout having to replace all with sourcing rules.

Has anyone hit this problem before?