It is if you have a user access token from the broadcaster.
You get a key from the broadcaster with the relevant oAuth scope(s)
Viewer logs in that gives you their userID
Then call
https://api.twitch.tv/helix/subscriptions?broadcaster_id=broadcaster_id&user_id=userID
And specify the broadcasters auth key you collected earlier (using the refresh token if you need to refresh).
You don’t need to request “subscription read” from the user if you have the broadcasters key with “subscription read” attached.
This is how I do it.