We report Raman investigations on stable and metastable phases of cyanoadamantane plastic crystal, which gives an orientational glassy state upon a deep undercooling below 175 K. The isothermal transformation of the metastable quenched plastic phase is systematically analyzed for quenches in the 180-250 K temperature range. Two different kinds of ordering process have been evidenced, depending on the depth of the quench. For shallow quenches (above 200 K) the ordering process is characterized by sigmoidal growth curves corresponding to the nucleation and growth of the ultimately stable state. For deep quenches (below 200 K), atypical kinetics laws are observed. In this case the system escapes from its metstable disordered state preferentially via the transient development of domains whose structure slightly differs from that observed in the ultimately stable phase, in agreement with Ostwald's rule of stages. The development of this local structure, after quenches at temperatures approaching T-g, is considered to be responsible for the extension of the lifetime of the metastability of the plastic phase and then could be at the origin of the glass formation.