It was reported before that the nurses were not kidnapped, but moved from ISIS, because the safty couldn't be guaranteed anymore. The fact that they had access to their phones also shows that they weren't really hostages, that were taken to ask for ransom or similar goals.
That doesn't fit to the picture the ISIS get in the bulk of the media reports, but there are also reports that they took over and "running" banks and power supply, just as armed ISIS "soldiers" were seen to take over basic jobs that a normal traffic police usually do. So they show not the usual habbits of terrorists and actually seems to want to run a state or the region in a proper way and even with more respect to foreigners and women compared to the Taliban in Afghanistan. The problem however is, one can't say at this point if that was only one ISIS group that had shown this habit and if others acted different (alleged mass killings of opponents, still captured Indian men that wasn't released so far, openly threatening India and other countries), so things are changing day by da and one can't actually say how they really are, at least imo.
Its their Honeymoon period. They will lay waste to everything once they consolidate power to decorate it like it was in 700ad. All you have to do is go back a few month when they were honeymooning with the FSA. Now they want to run the show on top on their heads. Literally.