Yes. They can.
However prior notice about the intention to transfer the foreground must be given to the other project partners together with sufficient information concerning the future owner so as to permit them to exercise their access rights. Transfer of ownership is generally allowed, as long as the obligations regarding that foreground are passed on to the transferee.
Where a participant does not intend to protect a piece of foreground, it should firstly offer to transfer it to other partners. Whether none of the participants intend to protect foreground, they might transfer it to third parties (the inventor, for instance) which may consider worthwhile protecting it, rather than leaving it unprotected and available for use by competitors (Article 44.2 of the Rules for Participation and Article II.28.3 of the Standard Grant Agreement)
These issues may be covered in detail within the consortium agreement or through specific separate arrangements.