A G1159 had a conflict with a light aircraft during traffic pattern entry at 1;500 FT. The traffic had been reported by the Tower and generated a TCAS RA. The Captain; who was pilot flying; did not take evasive action.

Narrative

Once in level cruise flight while in VMC; Center advised holding due to delays in the area. The Captain [requested] to proceed VFR; but only as long as we could receive advisories. ATC approved and the Captain initiated a VFR climb to 13;500 FT. During the descent phase of the flight; the Captain maintained airspeed in excess of approved limits for the airspace. While I was speaking with the local controlling agency; the Captain called Tower to check in and request advisories well in advance of nearing the class D airspace. After being instructed a frequency change and RADAR services terminated; I checked in with Tower five miles southeast of the field for a left downwind entry. I was advised to report a three mile final. I then asked if there was traffic in the area and was advised of south-westbound traffic down the shoreline at 1;500 FT. While attempting to locate the traffic; the TCAS instructed a resolution advisory to climb. The Captain did not respond to the RA and maintained course and altitude until soon after spotting the aircraft. I had not spotted the aircraft until within close proximity and discovered it to be of the single engine low wing type; passing just underneath the starboard side of the aircraft at the 2:30 position; head on. After landing; the Tower advised [us that] Center had called and advised that we had operated within close proximity to another aircraft. The Captain instructed me to respond as 'to having the aircraft on TCAS; but not ever having a visual on the aircraft itself.'