Interesting thread. One of the smaller OEMs recently raised a few eyebrows by suggesting that passive (as opposed to laser) wire detection systems were a better solution than cutters. The obvious downside pointed out by EN48 is the first problem; the second is that, with a max usable detection range of 500 ft, you only get two seconds warning, which is not much (esp. in low-viz conditions).
I'd maybe take both systems together, but I wouldn't want to give up my WSPS.
Vertical Freedom - The best-known passive system is probably Safe Flight's PDS. The EADS HELLAS, Elbit SWORD and Selex LOAM systems would offer better detection, but are unlikely to be affordable for survey work in their current forms.
I/C