POTENTIAL RWY INCURSION WHEN A TAXIING B737 PIC IS NOT CERTAIN THAT HIS TAIL IS CLR OF THE RWY HOLD SHORT LINE FOR RWY 22R ON TXWY G WITH AN ACFT ON TKOF AT EWR.

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NOT SURE IF THIS WAS AN INCURSION OR NOT; BUT IT WAS AT THE VERY LEAST A POTENTIAL PROB. WE HAD LANDED ON RWY 22L AND WERE TOLD TO TAXI TXWY N ON TXWY P TO HOLD SHORT OF RWY 22R AT TXWY G BEHIND ANOTHER ACFT Y. TWR THEN CROSSED BOTH OF US ACROSS RWY 22R AND TOLD US TO HOLD SHORT OF TXWY A ON THE OTHER SIDE. IT TOOK ABOUT 2-3 MINS FOR THE ACFT Y IN FRONT OF US TO GET THROUGH TO GND CTL AND BEGIN TAXIING TO THEIR GATE. MEANWHILE; WE WERE AS CLOSE TO HIM AS POSSIBLE; BUT I'M SURE OUR TAIL WAS STILL TECHNICALLY IN THE RWY ZONE WHEN I SAW AN ACFT Z BEGIN THEIR TKOF ROLL ON RWY 22R. I IMMEDIATELY ADDED PWR AND 'SNUGGED' UP DIAGONALLY AS CLOSE AS I COULD TO THE ACFT X IN FRONT IN ORDER TO TRY AND PULL OUR ACFT X COMPLETELY OUT OF THE RWY ZONE AS THE TKOF ACFT Z WENT BY. WERE WE AN INCURSION ACFT? I DON'T KNOW; BUT TWR SHOULD KNOW BETTER THAN TO CLR AN ACFT FOR TKOF WHEN THERE ARE 2 ACFT ON THAT SHORT TXWY G. I KNOW THAT WE ARE EXPECTED TO CLR THE RWY ASAP WHEN WE ARE CLRED TO CROSS; BUT HOW CAN YOU WHEN THE ACFT IN FRONT OF YOU CAN'T MOVE?