Hetzner pre-provisions systems. If you're a existing customer in good standing and don't have special wishes (e.g. you don't enter something in the "comment" field of the order) your system will be ready in ~5-10 minutes.
They build their own PXE setup and assemble the hardware themselves. iirc they have >100.000 physical servers on 2 locations. Each location consists of ~10 buildings like described here: http://www.datacenterpark.de/images/rz_modell.gif
