The heterometallic Mg-Ti butoxide catalyst was successfully used to synthesize telechelic macromonomers containing urethane-ester cleavable linkages and methacrylic photoreactive terminal groups suitable for photopolymerization towards elastomeric polymer networks. The concentration of the catalyst during the synthesis of macromonomers strongly influenced the reaction kinetics, degree of acrylation, average molecular weight, and dynamic viscosity of the obtained products. As a result, we observed marked differences in the physico-chemical, thermal, and thermomechanical properties of elastomeric films obtained during photopolymerization of the macromonomers. The curing atmosphere (air vs. argon) also had effect, particularly on the dynamic thermomechanical properties of obtained polymer networks. Importantly, all of the obtained materials demonstrated high cell viability in extract tests according to ISO 10993-5, independent of the catalyst concentration and curing atmosphere. As a result, we conclude that the heterometallic Mg-Ti butoxide catalyst can be a good candidate for replacement of homometallic catalysts for the synthesis of urethane-based precursors for photocured elastomeric networks for soft tissue biomedical applications.