AN EXPERIENCED COMMERCIAL PLT TAXIED ACROSS THE ACTIVE RWY WITHOUT A CLRNC BECAUSE HE DID NOT KNOW THAT THE ARPT HAD RECENTLY BECOME TWR CTLED. THE RPTR STATED THAT HE DID NOT GET A STANDARD PREFLT BRIEFING FROM FSS AND HE DID NOT RECEIVE INFO FROM THE FBO OR SEE ANY SIGNS REGARDING THE NEW CTL TWR AT THE ARPT. ALSO; THE NEW TWR STRUCTURE WAS NOT HIGHLY VISIBLE.

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NEW TWR AT GWINNETT COUNTY (LZU). TWR CAP NOT ON TOP OF STRUCTURE; BUT IN USE. NO INFO AT THE FLT SCHOOL WHERE THE ACFT WAS RENTED THAT A TWR WAS IN USE. ANNOUNCED INTENTIONS ON UNICOM; TAXIED OUT TO RWY 7; XING RWY TO GET TO OTHER SIDE FOR TAXI. FLT SCHOOL CALLED ON UNICOM; SAID TO CALL GND NEWS TO ME. GND CTL SAID NO PROB; HE WAS WATCHING ME SINCE START OF TAXI. HIS COMMENT WAS FLT SCHOOL SHOULD POST NOTICE TO RENTERS THAT THE TWR IS IN USE. I STRONGLY AGREED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE TWR HAD A 'HEADS UP' ON THIS RPTR AS HE CROSSED THE ACTIVE RWY (SO THAT HE COULD DEPART FROM THE RWY THRESHOLD). THE ATCT LCL CTLR TOLD THE PLT THAT IT WAS NO PROB; AND THEN CLRED HIM FOR TKOF ON RWY 25; INSTEAD OF RWY 7. THE PLT HAD BEEN COMMUNICATING ON THE CTAF SINCE HE BEGAN TAXIING ON THE RAMP. THE INTERRUPTION CAUGHT HIM TOTALLY BY SURPRISE. HE STATES THAT HE KNOWS THAT HE SHOULD HAVE CALLED THE FSS AND CHKED THE NOTAMS; BUT THAT HE WAS JUST GOING OUT FOR A LCL 1/2 HR FUN FLT. RPTR ALSO CONTACTED TWR CTLR AFTER LNDG BY TELEPHONE AND WAS TOLD THAT THERE WAS NO CONFLICT.