hmm, this quest comes up every year.
engine makers do not want you to power back on reverse, because you take dust and sand and any sh* from the ramp into the engines and you gonna blame them in a guarantee claim later on. what you always do, is taking the risk of disruption of service and aog.
t-tail aircraft with tail mounted engines are better off for this, engines exhaust and intakes are farther away from the ground => less risk of FOD.
I believe, the power back is used on airports with special ramp conditions, i.e. the ramp is build with a one per cent slope (which is actually done for better rainwater evacuation). backing on reverse thrust on the slope isn't using high engine power setting thus reducing risk of FOD. example I was told: Atlanta ?