I do not have first hand knowledge of the process, but from what I have read and assumed over the years, most breweries have pilot brew systems, which are similar to large home brew setups. I know Sabco is now marketing the brew magic this way. Once the brewer is happy with a recipe at this scale, they may then do a single run on the regular brew system and release as a special beer or tasting room only product. Depending on public reaction, it may make its way to a seasonal or full time release.