Hey guys I just want to chime in for those wondering about this job. I've worked with Jon and ATP on and off since 2009, most recently for a 6 month stint over 2014-15. They are really dedicated to raising the bar for arboriculture in Hong Kong and Asia as a whole, and if you work for them you will come away richer for the experience.
Some of the places you'll work and trees you'll work on are really spectacular, and the quality of life in HK is quite high. There's tons of green space for hiking and rock climbing, even good beaches for swimming and surfing. The urban areas are very safe, although much more crowded than American cities.
If you haven't worked in the tropics or the Asia/Pacific region before you'll probably have to learn a lot of new trees, and if you haven't spent a lot of time using sonic tomography and resistance drilling, you will.
It's definitely not for everyone, but for the right person this is a killer opportunity.