There aren't any circumstances I am aware of where TAWS lets you descend with less terrain clearance than that provided by published routes and procedures, or permitted under ATC radar vectoring, or under ATC procedural safe altitudes, or under the off-route 1000' terrain clearance rules.
TAWS is warning system to reduce the risk of flying into terrain if something goes wrong with the normal IFR practices. It's not a navigation system.
brgds
421C