It's a recipe for disaster until those sprinklers are installed. I remember this fire in Waltham from a few years back:
Massive fire engulfs Waltham construction site
<p>A windy Sunday morning helped fan the flames of a massive fire in Waltham, destroying five buildings at a construction site. </p>www.boston25news.com
I lived just a half-mile away at the time, and that morning was quite intense in downtown Waltham. It's worth remembering that it was an utterly futile & senseless gesture--if the arsonists were disgruntled subcontractors on the project, "complaining" about working conditions, they accomplished absolutely nothing in terms of sabotaging the project, which immediately got rebuilt (and presumably the developer was made 100% whole via insurance).
The gesture was also criminal, beyond the strict legal definition of "arson," in that it was done in a very high density neighborhood, on a fairly windy, dry day, and if any of those sparks/embers had caught on the surrounding wood-built neighborhood--yikes.