There are a number of specialist contractors who offer this service at a very low cost (ranging from $120 to $250 per km dependent upon size of contract and location). If a water utility is big enough to carry out leak detection surveys constantly then it might be worth purchasing the equipment, but for most regional water utilities the cost of the equipment makes it uneconomical (except at EOFY when money needs spending!). I suppose it is not so much the money it is probably harder to keep staff trained to get the most out of the equipment. The vast number of small water utilities have leak detection equipment somewhere in a cupboard or locker that has not seen the light of day for many years as no-one knows how to use it!
It is a much better option to establish a monitoring regime that tells you when you need to undertake leak detection and in which areas. You may find that your system does not need to address leakage in many areas, but a couple of weaker parts of the system require Active leakage Detection on a more frequent basis. By setting up permanent monitoring you can proactively determine when this exercise will deliver significant return on investment. This way you address leakage as soon as it occurs and don't go looking for leaks when they are not there.
Happy to supply lists of leak detection contractors from big players to small one man bands that have all delivered good results for me whilst delivering water savings projects with over 60 local water utilities for the federal government.
Also happy to discuss in more detail if anyone wants to contact me.