Experimental and theoretical investigations are reported to comprehend the structural and lattice dynamical properties of high quality Bridgman grown zb Zn1-xMnxTe (x <= 0.15) crystals. Our detailed far-infrared reflectivity and Raman scattering measurements ascertained atypical "intermediate-phonon-mode" behavior for the alloys. Besides perceiving ZnTe- and zb MnTe-like LO and TO phonons, a weak Mn alloy-disorder mode near similar to 205 cm(-1) is observed. A classical "Drude-Lorentz" model is used for evaluating the dielectric tensors of ternary alloys to simulate composition dependent reflectivity spectra - providing results in good agreement with the experimental data at near normal incidence. Lattice relaxation effects around Mn-z(n) and Zn-m(n) from the synchrotron radiation extended x-ray absorption experiments are meticulously incorporated to help construct the perturbation models for simulating impurity modes using a realistic rigid-ion-model in the frame work of an average t-matrix Greens function theory - reconfirming on much firmer ground - the observed intermediate phonon mode behavior.