I agree with the build a platform idea. I haven't trapped them out of trees, yet, the vacum idea will get a bunch of bees but how close to the hive can you get to get in there and vacum them off the combs, probably not close enough. Trapping them out seems to make the most sense here. M.B. has some good advice on his site about this issue and I believe Jerry as in Jerrymac has done a bunch of trapping. The only thing with trapping is that it takes quite a while, like several weeks. I have used beequick, it smells good and will drive the bees out, but probably not the queen. Once things settle down, the bees will want to go back into the tree, so you need to have a good plan formulated.
An idea, which others can add to. Build platform, have a hive body ready, maybe two. Seal off the tree, make hole for bees to escape, place cone over hole. Drill a hole on the back side of the tree. Blow the Beequick in use theexhaust of a vacum to do this by placing a rag or cloth over the end of the hose dampened liberally with Beequick. The idea is to force the bees out and into your awaiting hive. It would be really nice to have a frame or two or three of broodcomb from another hive in the box you will be driving the bees into. You will not get any broodcomb from the tree and probably not the queen. I would if I could, do this when the temps are up, so your new box's brood don't become chilled. This is where others who have actually done this can chime in, because I'm not sure what the next step would be, if you simply remove the hive at this point or leave it there for a day or more, in hopes that you would get the queen to move out, I just don't know at what point you would remove the new hive. If time was of the essence, I would drive them out, let them settle into the box, that evening, seal the entrance and move them. Don't forget you will have to seal the holes in the tree or you WILL have other swarms settle in the tree again, at some point. Of course you will need to have a queen ready for this hive, unless you get lucky and get her.
Best of luck, JP