The present paper focuses on laboratory tests of resistance to severe environmental conditions performed on prototypical under ballast mats (UBMs) according to the procedure described in the European standard EN 17282, which was introduced at the end of 2020. Most of the analyzed samples of UBMs were based on elastomeric materials from recycling, such as styrene butadiene rubber (SBR) granulate and fibers from recycled waste tires and rebond polyurethane from polyurethane waste, and additionally, for comparative reasons, one of the tested UBM samples was based on mineral wool. It was proved that in the case of mineral wool- and polyurethane-based samples, there are significant differences in static and dynamic characteristics determined before and after the resistance tests and permanent deformations are observed. Elastomeric mats based on recycled rubber exhibited good properties in the performed tests and thus, they should be regarded as effective and durable vibration isolators which can be used to protect people and the surrounding environment against structure-borne noise and vibration generated by railway traffic. The results of experimental tests were additionally used by the authors to create a viscoelastic model of the vibration isolator (UBM) with fractional derivatives. Using the original model of the ballasted track structure with four degrees of freedom, a significant influence of severe environmental conditions together with the dynamic cyclic loading on the level of vibration suppression (insertion loss factor) was demonstrated. Additionally, the authors proposed the assessment criteria for the resistance to severe environmental conditions of UBMs, tested according to the new standard EN 17282.