As mentioned by aileron 69, UTS were definitely not the only survey company to bid on the project. All the survey companied would have tendered on all areas released by GA last year and the surveys awarded primarily on price. If UTS quoted using single pistons as opposed to other companies tendering using other equipment then it was likely they won on price.
All the companies are desperate for work at the moment but hopefully they maintain their safety standards although it makes it difficult when other companies start dropping theirs.
As far as I am aware, UTW was actually flying an onshore section between Caiguna and Cocklebiddy although they were also flying offshore sections with single pistons as well, although, UTS are not the only company to do this. GPX had an incident in Horn Island early in the year with a C210, and in all likelihood this survey would have been offshore as well.
It would be interesting to see their Risk Assessments for these projects. It is a requirement of GA tenders that these be submitted with the tender documents and that the companies are members of IAGSA, although IAGSA is bit of a toothless tiger at the best of times.