If you have an active root...over time it will grow back in there unless you excavate, cut and remove. 

It's just unfortunate you were not notified to get the plumbers out sooner or the PM did not communicate not to leave the faucets off but ultimately if they were left off you likely would have had pressure built up and pipes burst (especially if they lines weren't all PEX) so the root issue of not having heating water lines still was the issue.

Generally no because the root system is still in place.

I'm rooting for you, and for your project to have success!

Can anyone recommend good companies to root cause  and implement solution to fix this issue?

I would say on a rental property that's unrealistic, if it really is an issue on a property, better to address the root cause.

I guess I can't wrap my head around the fact that anyone can make an argument as to how the doors and windows being left open was not the root cause of this issue.

All of my family grew up near Baton Rouge and went to LSU, so I'm rooting for you.

I'm rooting for this to be wrapped up! 

Some old Milwaukee sewer laterals have tree roots that like catch on to stuff.We also eliminate garbage disposals during rehab and normally we have someone from our team check out issues, before we send a plumber.