We show that the numerical code used in the above mentioned paper does not take into account the multiple scattering effects of electromagnetic fields properly and is, therefore, incorrect.
related article: http://dx.doi.org/10.1016/j.nimb.2007.01.130

Nucl. Instrum. Methods Phys. Res. B

Gevorkian, Z. S., & Verhoeven, J. (2008). Comment on the paper "Radiation induced by relativistic electrons propagating through random layerd stacks : numerical simulation results" by Varfolomeev et al. [Nucl. Instr. and Meth. B 256 (2007) 705]. Nucl. Instrum. Methods Phys. Res., Sect B, 266, 1137–1138. doi:10.1016/j.nimb.2007.12.060