It would be interesting to get more details about the tunnels, and their length, depth etc. Some of the tunnels would have been dug before the arrival of Bushell and the consolidation of the escape activities into one big break. A lot of tunnels in a lot od camps were quickly abandoned because they were unsuitable, or the diggers got frustrated and gave up, were discovered, or the diggers were transferred.
Others would have been dug by individualists (not all escape plans were put to the escape committe, and sometimes POWs carried on without "official" approval, even after the three main tunnels were started).
And some of the tunnels would probably have been more like chambers to store escape equipment and contraband.
This is a great site on the escape:
http://www.elsham.pwp.blueyonder.co.uk/gt_esc/