Google’s continuous audience sharing was announced last year, allowing manager accounts to share audience lists with a sub-account. More recently though, the search engine allowed sub-accounts to return the favor by being able to share existing and future remarketing lists with manager accounts automatically.
Although being able to share lists between sub-accounts and the main account is useful, there needs to be some level of precaution taken. If you share lists without permission from another account, it would cause trouble with that account holder.
Basically, just make sure you get permission before sharing anything.
Source – Search Engine Land