ANY licensed Real Estate Agent can show you ANY house publicly marketed, regardless of the companies involved.
Once an agent becomes licensed, they join the local Board of Realtors, and we all have the same access cards (i.e. smart cards) which allow us to open lockboxes that are used by everyone (whether combo or electronic).
So don’t worry…whatever agent you choose to work with, will be able to show you ANY house you want to see! Likewise, if you’re selling, any agent will be able to show your home to prospective buyers.