I wouldn't advise it. They might live, if you get a good rootball on them, and they are watered well, but with a greatly reduced root system, the reason these trees often die when planted during candle growth is that even with ample water supplies, the roots cannot pull up water as fast as the transpiration and new growth (both of which are accelerated in warmer weather) need it. The plants dry out rather fast, especially on sunny warm days. It's best to wait until the new growth has hardened off some, if you can't get them in before bud break (as in your case).
You could warn the client of the possibly low success rate, and let them decide, knowing that planting now could mean gaps and/or replanting. But that's quite some capital to put at risk like that. I'd recommend that you wait until the construction etc is over if possible, even if that means the trees go in a year late.