I was flying from AMS to BGO on KL1185 last Friday on B737-700. We were taking off from runway 24, entering via taxiway S7. While we were approaching the runway, an Easyjet A319 was holding in position on 24, he entered on S6 before and was waiting on the runway. Now, the distance between S7 and S6 is not that much, probably 100 meters or so (if you consider that the U2 stayed as close to S6 as possible on the runway to have as much TORA as possible).
What really surprised me was the fact that we didn't hold short of 24 at S7, but entered right away. While aligning with the runway heading, I could see from my window that the Easyjet was still holding in position and didn't start it's take-off run yet. He actually started its take-off, when we were already holding in position right behind him on the runway. The distance between the two planes was only a little less than that of S6 to S7.
I know that when a plane in front of you starts its take-off roll, you usually enter the runway as quickly as possible. Also that sometimes you cut the line via an earlier taxiway to enter the runway, when you are losing your slot and there's a large queue at the main entry point. But I have never heard of 2 aircraft holding behind each other on the runway, before the first one even started its take-off roll.
So, I hope you understand the scenario I'm describing. This was something I never experienced or heard of before, so can somebody please shed some light onto this? Is this a common practice?