The Registry for .nl (SIDN) and the Registry for .be (DNSBelgium) offer the option to transfer and restore a domain which is currently in quarantine at a different registrar. This process can not be done via the control panel, but can be requested via the support department via support@openprovider.com as it requires manual processing.
The costs for the transfer + restore is € 75 (per domain, excl VAT) 

Requirements for a .be transfer from quarantine:

Add the following details in the email:

• the domain name
• a valid authorization code (can be requested at the Registry)
• the handles (owner, admin, tech, billing) matching the current whois details
• nameservers
• awareness and approval of the fee

Requirements for a .nl transfer from quarantine:

Add the following details in the email:

• the domain name
• the handles (owner, admin, tech, billing) matching the current whois details
• nameservers
• awareness and approval of the fee
• proof that the registrant wants to transfer the domain name to Openprovider (for example, an e-mail)
• proof of ownership (available here, more information available in our .nl article (Transfer > Proof of ownership))
• identification documents:
  • If the registrant is a natural person:
    • a copy of the identity document of the registrant
  • If the registrant is a legal person (company):
    • a business registration document from the Chamber of Commerce (not older than six months) from the registrant
    • a copy of the identity document of the person authorised according to the business registration document