OPERROR LOSS OF SEPARATION.

Narrative

SHORTLY AFTER BECOMING AIRBORNE TWR TELLS ME THERE'S A 'B727 OFF THE R RWY ON CLB OUT FOR A N DEP.' SURE ENOUGH I'M LOOKING AT Y AT 1 O'CLOCK; 1.5 NM; SLIGHTLY HIGH. I RPTED HIM IN SIGHT. AND THAT WOULD HAVE BEEN THE END...EXCEPT WE'RE BELOW HIM; CLBING AT A GREAT RATE AND OUT ACCELERATING HIM -- AND PLANNING A NE DEP; TOO! I ASKED DPE WHAT HIS (Y) ENRTE AND CLB LIMIT CLRNC WERE? '...15000 FT AND NE' WAS THE ANSWER. BY NOW WE'RE SHOWING A TCASII TA AND WE'VE 'BUGGED.' THE AIRSPD BACK FROM 250 KIAS TO VZF (220 KT) TO EXPEDITE THE CLB RATE AND REDUCE CLOSURE. HOWEVER; NOW Y IS NOW TURNING N! AS I'M LOSING SIGHT OF Y UNDER THE NOSE (ABOUT 2000 FT BELOW US) I RPT TO DEP WE'RE NO LONGER ABLE TO MAINTAIN VISUAL CONTACT. ONLY NOW DO THEY (DEP) SEEM TO GRASP THE SEVERITY OF THE SIT: ISSUING US A VECTOR; OFF COURSE AND Y AN ATTITUDE CAP (BELOW US). SURELY THIS IS NOT STANDARD PROC! PERHAPS THE PROB WAS CAUSED BY THE PERCEPTION THAT 'A JET IS A JET;' NOT REALIZING THAT NEW JETS OUT CLB OLD JETS; ETC. RELEASING 2 ACFT TOWARDS THE SAME POINT AT THE SAME TIME COULD SPELL DISASTER!