"Can Niantic detect when you switch accounts "regularly"?"

#PokemonGO: I know you should not multiaccount, but my little brother lost his phone and now just has an old phone which does not run Pokémon Go until he gets a new one. Can I switch into his account on my phone for rare catches and to keep his streaks going or will niantic detect that I regularly switch accounts and therefore ban (both?) Accounts? I've been told by someone in our local park that they can't track it somehow or can't do it here in Germany for some technical reason I can't remember. Anyone knows something about this? Thanks! via /r/TheSilphRoad http://ift.tt/2GHRQa6