Currently, at the start of an online battle, all the opponents' team data is sent to each player. This means they can see what Pokémon their opponents has, what moves those Pokémon have, etc. which goes against the grain of the game a little. However, this would undeniably be a lot of work to deal with.
Currently, at the start of an online battle, all the opponents' team data is sent to each player. This means they can see what Pokémon their opponents has, what moves those Pokémon have, etc. which goes against the grain of the game a little. However, this would undeniably be a lot of work to deal with.