The general answer is no, since you have a lot of chemstry going on in N2/H2 plasma: Some molecules will be dissociated while other compounds are formed. You can get not only ammonia but also, for example, hydrazine (N2H4), hydrogen azide (HN3) or ammonium NH4+ in different concentrations and along different reaction paths in each plasma.
In many cases the reaction paths are not only dependent on the plasma you create (i.e. its chemical compounds) but also on the way you create it: rf, microwave, DC, pulsed DC, etc.
I am afraid the answer is no, in general. Should the absorbed power be sufficiently high in order to fully dissociate and hence ionize at least partially all components it could be yes. But when it is not the case, the previously provided answer prevails. Moreover, when considerable H2 / N2 components remain, they don't behave as the NH3 one. A dedicated Detailed Global Model (DGM) could provide a better insight.
As ZZ points out, NH3 plasma contains more molecules and less ions when the absorbed power, hence the temperature are low. The same will be true for the H2 / N2 mixture plasma. DGMs describe in detail the road to ionization, but in general for plasma based to molecular species and for low absorbed power, substantial part of the absorbed energy is spend to dissociate the molecule(s) rather to ionize, changing the chemical consistance.