Yes. If you have a subscription pass (either a Premium or Frequent Pass), you automatically join Club Eurostar. 

- As a Frequent Pass subscription holder (6 and 12 months), you gain direct access to Avantage tier.
- As a Premium Pass subscription holder (6 and 12 months), you gain direct access to Etoile tier.

As a subscription pass holder you benefit from reduced prices and flexible ticket conditions LINK TO "What are the features of the Frequent Pass and Premium Pass subscriptions?", for travels between Belgium, France, The Netherlands and Germany.