From the CEO's address THL sys it has a market dominant position and a well defined strategy. The address also says:

"Although the yields are currently challenging, Explore More and our rebranded Backpacker product has gained market dominance and has curtailed the growth and product mix of competitors. More importantly, we have extended the useful rental life of our smaller vehicles in preference to selling them to low cost start-ups.
Over the next 12 months we will continue to grow our discount product offerings particularly, as we are seeing signs of consumers chasing value in the tighter economic environment."

To me, that implies that the biggest threat to yield in the Maui and Britz brands are the expanding Explore More and Backpacker brands.