It completely depends on who, what, when, where, and why. The paperwork for why you are on probation, and lets face it, your probation officer may speak with the employer. Attitude, and their risk/benefit is going to be the decider.
Your probation officer most likely will need to talk to the company. Depends on your charges, age, risk of re-offending, and various other things. Although most probation officers, and parole officers(myself included) are quite strict with our curfews, which will be a pain due to you working ems and will most likely have weird hours. HIGHLY CASE SPECIFIC...