Commercial-off-the-shelf Bipolar Junction Transistors (BJTs) are commonly used in critical radiation-tolerant electronic systems, making their radiation qualification essential to ensure compliance with project-specific radiation design requirements. Although the response of BJTs to radiation is well-documented, their sensitivity to Total Ionizing Dose (TID) and Displacement Damage (DD) can complicate their qualification for systems exposed to diverse radiation environments, such as high-energy particle accelerators. This work investigates the primary degradation mechanisms in various BJTs used in CERN electronics, where devices are exposed to neutron-rich and charged particle environments. This research supports the adaptation of qualification strategies, ensuring a more reliable prediction of BJT degradation in complex radiation environments. The paper also provides examples of system response estimations and highlights the impact of various degradation mechanisms, such as lot-to-lot variations, Enhanced Low Dose Rate Effects (ELDRS), and how the relative dominance of TID or DD effects can differently affect both system performance and the qualification process.