https://www.battlefield.com/news/article/introducing-premium-friends-a-word-from-our-producer
We call it Premium Friends. Here’s how it works:
As a player who owns Battlefield 1 Premium Pass you will be able to bring
your friends in Battlefield 1 along to play on the new maps!
When creating a party in Battlefield 1 you may notice something new: if
someone owns a Battlefield 1 Premium Pass the party will become "Premium
Enabled". This will allow anyone in that party to play on all maps,
regardless if they own the content or not. The access is available as long
as the party is "Premium Enabled".
While all players will be able to play on maps accessible
through Battlefield 1 Premium Pass through Premium Friends, some
experiences are exclusive to Battlefield 1 Premium Pass owners.
- In a “Premium Enabled” party, only owners of a Battlefield 1 Premium
Pass or the specific expansion pack will earn XP from the maps exclusive to
that expansion. We will save the XP for everyone else and grant them
retroactively if they decide to get the Battlefield 1 Premium Pass for
themselves.
- Only owners of a Battlefield 1 Premium Pass or the specific expansion
pack will be able to spawn in with weapons and vehicles unique for the
expansion.
- Only owners of a Battlefield 1 Premium Pass or the specific expansion
pack will track progress towards the unique medals and codexes for the
expansion
