WHILE ON A REPOS FLT; AN AIR TAXI FLC HAD TAXIED ONTO THE RWY; BUT DELAYED TKOF AS A RESULT OF A MECHANICAL PROB. DURING THE DELAY A GND VEHICLE DROVE ONTO THE SAME RWY AND APCHED THE FLC FROM THE OPPOSITE DIRECTION. WHEN THE FLC BEGAN THEIR TKOF; THE VEHICLE WAS NOTICED AND THE TKOF ABORTED. AT THE SAME TIME THE ATCT LCL CTLR ANNOUNCED ON FREQ THAT THE TWR WAS OPEN.

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PART 91 RELOCATION FLT WAS TO DEPART BEFORE THE TWR OPENED AT XB00. TOOK RWY FOR TKOF AT XA57. REMAINED ON RWY FOR A FEW MINS TO CORRECT PRESSURIZATION MALFUNCTION. PROPER CTAF RADIO CALLS WERE MADE AND WE WERE MONITORING THE TWR FREQ. BEGAN TKOF ROLL AND AT ABOUT 70 KTS WE PERFORMED A REJECTED TKOF. THERE WAS A SECURITY TRUCK WITH LIGHTS ON; APCHING FROM THE OTHER END. HE WAS PERFORMING A RWY CHK. DID NOT GET ANY CLOSER THAN 2500 FT. TWR CALLED US AND SAID TWR WAS OPEN. WE HEARD NO OTHER CALLS. SUPPLEMENTAL INFO FROM ACN 332895: I WAS THE PNF. THE CTL TWR WAS CLOSED SO I ATTEMPTED TO GET OUR CLRNC TO EAGLE COUNTY FROM REGIONAL APCH CTL ON THEIR FREQ. I ATTEMPTED SEVERAL TIMES WHILE ON THE RAMP; WHILE TAXIING AND AT THE DEP END OF RWY 33. (AS WE LEFT THE FBO'S RAMP OUR #1 COM RADIO WAS TUNED TO REGIONAL APCH AND #$2 TO ADDISON TWR.) WE TAXIED INTO POS WITH LNDG LIGHT; NAV LIGHTS; STROBE LIGHTS; AND ROTATING BEACON ON AND WERE MONITORING TWR FREQ. WE PROCEEDED TO TAKE OFF. WE ROLLED APPROX 1/4 OF THE RWY WHEN I SAW WHAT APPEARED TO BE A VEHICLE'S HEADLIGHTS COMING TOWARD US ON THE RWY I SHOUTED 'ABORT.' I IMMEDIATELY ANNOUNCED; ON TWR FREQ THAT WE HAD ABORTED THE TKOF. I LOOKED AT MY WATCH WHICH SAID XB00Z.