Dear Povall,
Microsoft Teams has been gradually rolling out updates, and features can change. As of the latest updates, live captions are indeed available in breakout rooms. This feature helps make meetings more accessible by providing real-time captions during breakout sessions.
Read more on this blog article: https://techcommunity.microsoft.com/t5/microsoft-teams-blog/what-s-new-for-microsoft-teams-rooms-and-teams-meetings-at/ba-p/3843949
Hope this helps.
Thanks,