Based on a lattice model describing the elastic phase transition for ferroelastic-martensitic transformations, the set of nonlinear difference-differential equations derived in the preceding paper (I) governs the shearing motion of the atomic layers (11\ifmmode\bar\else\textasciimacron\fi{}0) stacked in the [110] direction. A quasicontinuum approximation is developed in order to incorporate the leading discreteness effects of the lattice system. The method using the Fourier images of discrete functions leads to a continuum model where macroscopic and microscopic stresses can be deduced from an elastic potential involving a strain gradient. After introducing appropriate boundary conditions on the stresses at each end of the lattice, nonlinear excitations modeling elastic structures are investigated. Then, the quasicontinuum version provides the following results: the existence of (i) quasiperiodic strain waves corresponding to spatially modulated structures, (ii) an array of strain solitary waves representing periodic arrangements of martensitic-austenitic domains, (iii) martensitic or austenitic solitary waves relating to the shearing motions of atomic planes along the stacking direction, and (iv) a static twin interface between martensitic and austenitic domains. The importance of the competing (bending forces) and discreteness effects included in the quasicontinuum model is emphasized to show different regions of existence. Numerical simulations are performed on the microscopic model in order to ascertain the quasicontinuum model and to check the stability of the nonlinear elastic structures. By way of conclusion, comparisons with other works or approaches, as well as extensions of the model, are discussed.