i think laddering up to the scaffolding of a tree; especially if you are going straight up only or within 25' of ladder is a fair strategy; to simple to negate. i've leaned away from ladders etc.; but seeing as you might need one for groundie roof access anytime; have cussed mys-elf for not having one a few times. Then, once it is there; might as well use it intelligently.
i wish those that insist on spiking, would use ladder for 1st 25-35'; then observe how much of the Natural scaffolding of the tree would allow them not to spike. This would be better for the tree health, better visual quality for the customer; and perhaps wean more folks off of spikes; give them confidence to start not wearing them on some jobs, feel lighter on their feets etc.