It depends on the probiotic and the antibiotic. The more common oral bunny antibiotics (Baytril and Septrin) are used because they do little damage to most normal gut bacteria. The more modern probiotics specifically designed for rabbits contain some normal gut bacteria and high levels of saccharomyces, a yeast that is present in high levels in bunny guts. As yeast are fungi not bacteria they also survive most antibiotics.
The real question is whether probiotics can survive the incredibly acidic rabbit stomach as this is designed to kill any microbes coming in on food... In rabbits on certain medications (e.g. Zantac) stomach pH is increase and probiotics are more likely to be effective.
Marie