The interstellar detection of CH3CN metastable isomers would suggest that CH3NC and H2C═C═NH formed in star-forming regions through energetic processing provoked by shocks or others energy sources. In this context, laboratory simulations have been carried out to investigate the chemical transformation of CH3CN into CH3NC and H2C═C═NH induced by UV photolysis and high energy particle irradiation. In the present study, we have carried out the CH3CN + N solid state reaction in the 10–40 K temperature range in order to examine the behavior of acetonitrile interacting with nitrogen atoms in icy interstellar grains. We show that CH3CN + N is efficient in the solid phase but only in a very specific temperature range, which combines high mobility and relatively long surface residence time of N atoms to allow the CH3CN activation. By focusing on the behavior of [CH3NC]/[H2C═C═NH] abundance ratios versus temperature, we have measured abundance ratios around 10.4 at 10 K, which decreases to 6.8 when the temperature of the reaction increases. These ratios are of the same order of magnitude as those reported from acetonitrile isomers detection toward Sagittarius B2(N). In contrast, previous studies involving energetic processing of solid CH3CN, CH3NC and CH2CNH have found that they have been formed with [CH3NC]/[CH2CNH] ratios ranging between 0.3 and 1.7. Additionally, the analysis of CH3NC and H2C═C═NH column densities shows that at low temperatures, the less stable isomer is favored against the most stable one. These results are compared to the puzzling behavior of CN-containing isomers such as HNC, HCN, HCNO, and HOCN in molecular clouds.