B737-700
Flight Crew Last 90 Days 268
Confusion
Deviation / Discrepancy - Procedural Clearance; Ground Incursion Runway
Air Traffic Control Issued New Clearance; Flight Crew Became Reoriented
Airport; Procedure; Human Factors
Just prior to push; new ATIS came out which favored Runway 33 vs 15 for departure. Completed new takeoff data and called for taxi and was cleared by Ground to taxi to Runway 33 via Runway 26; with no hold short instructions. I taxied down 26 and I knew that I was not cleared to enter 33 but was unsure where to hold exactly as there is no hold short line painted on Runway 26 for Runway 33. Began to make a short left turn toward the departure end of 33 and as I was stopping at what looked like a hold short line; was told to stop there as well by Ground. We never crossed that line and there was no runway incursion; but after reviewing the airport diagram and company briefing pages; it appeares that was the hold short for 26 coming the other direction. Was cleared to switch to Tower and departed without incident. Not sure why we were cleared to taxi on 26 to 33 as there is no published taxiway to get to 33 other than back taxi on 33 which we were not cleared to do.  There was no further query from ATC on this event. I think to avoid this problem in the future with Runway 33 departures; all taxiing aircraft should be on the taxiway around the terminal which is properly marked with hold short lines.
B737 Captain reports being cleared to taxi via Runway 26 to Runway 33 at BUR but is unsure of which hold line is the correct one for Runway 33. After takeoff it is determined that a runway incursion may have occurred.