Oddly enough, a scant two weeks after ISIS drove Bashar al-Assad’s troops out of Palmyra/Tadmur, Assad’s air force is providing close air support for ISIS’s offensive in Aleppo Province:
The Local Coordination Committees reported confirmation of 83 deaths across the country, with 35 of them in Aleppo Province and 25 in Idlib Province.
Significantly, most of the Aleppo deaths were from regime strikes on Mare’ and Tel Rifaat, where rebels are trying to hold back the Islamic State offensive that surged over the weekend. Mare’ has been at the frontline for months, with the militants seeking to regain positions that they lost in early 2014 when battles erupted with rebel factions.
I guess Assad realizes that an ISIS-rebel fight is in his best interests right now.
The Foreign Exchanges Companion 
Assad’s ongoing policy of cultivating/laying off of ISIS has been pretty deliberate, but these strikes in particular seem coordinated. I think his guys saw what was happening and made the decision to launch air strikes in support.