MD90 FLT CREW HAS TKOF CLRNC CANCELED AFTER STARTING TKOF ROLL AT SNA.

Narrative

SNA TWR CLRED OUR ACFT INTO POS AND HOLD WITH ANOTHER ACFT CLRING DOWN THE RWY AND ANOTHER ACFT ON FINAL FOR RWY 29R. AS WE WERE GOING INTO POS SNA TWR TOLD US TO 'PWR UP' AND BE READY FOR IMMEDIATE TKOF WHEN ACFT DOWNFIELD WAS CLR. WE RECEIVED TKOF CLRNC AS WE WERE STILL GOING INTO POS ON THE RWY. OUR OPERATING PROCS REQUIRE AT SNA THAT WE WILL NOT RELEASE BRAKES FOR TKOF UNTIL BOTH ENG EPR IS AT LEAST 1.25 EPR WITH ENGS STABILIZED. JUST AFTER THE CAPT RELEASED THE BRAKES FOR TKOF; SNA TWR TOLD US TO 'CANCEL TKOF CLRNC' AND TAXI OFF THE RWY DUE TO LNDG TFC BEHIND US. AFTER RECEIVING THESE INSTRUCTIONS OUR ACFT WAS ON TKOF ROLL WITH MAX THRUST APPLIED TO OUR ENGS. I (FO) WAS PLT MONITORING (NOT FLYING). THE CAPT TOLD ME TO TELL HIM (THE CTLR) UNABLE. I RELAYED THE MESSAGE TO THE SNA TWR CTLR WE WERE UNABLE TO COMPLY SINCE WE HAD ALREADY STARTED OUR TKOF ROLL. THE CTLR THEN ISSUED INSTRUCTIONS FOR THE ACFT BEHIND US ON FINAL TO EXECUTE A GAR. I AM NOT SURE IF THE SNA TWR CTLR WAS AWARE THAT WE ARE PROHIBITED FROM MAKING A 'ROLLING TKOF' AT SNA FROM RWY 29R.