EU trademark registered in bad faith

Question

Company A has been using an unregistered trademark for 15+ years in the EU.

Newly established company B registers the trademark in EU, and sends a cease and desist to company A.

My understanding is that company A can can request EUIPO to invalidate or cancel the trademark registered by company B, if A can prove:

1. The trademark registered by B is identical or very similar to the trademark used by A.
2. B was aware of A's use of the trademark, before it filed for registration.
3. B intentionally registered the trademark to prevent A from using it i.e. bad faith (Article 59(1)(b) EUTMR)

While §1 is easy-ish to prove, what are the common ways to establish: 2. prior knowledge 3. intentionality