Yes, albeit with lower efficiency. Under unit assay reaction conditions, 10-fold more enzyme was required to achieve 10% conversion of a triphosphorylated 25-nucleotide RNA substrate to the monophosphate form than was required to fully decap the same 25-nucleotide substrate with a cap. A 100-fold excess of enzyme only achieved 50% conversion. For conversion of triphosphate to monophosphate, RppH (NEB #M0356) is a superior option.