This was a deliberate change made under CR 683458 in BCP version 15.7 ESD 4, to adopt SAP's more stringent "secure by default" policy.
A new feature has been developed that gives bcp a --filemode option that can be used to specify a less restrictive permission setting. This new feature becomes available in the connectivity 15.7 SP120 and 16.0 GA C1 releases.
Documentation: --filemode Option for isql and bcp
-bret