Erratum: There was never a restriction on collaborating only with professionals “not having participated in OSH projects before”, and the post has been corrected.
I held a wrong interpretation of the program’s terms, and I must apologize to anyone who might have not applied because of that mistake.
The call is still open! So they are also invited to apply 
(though I expect it to close rather soon).
As It was recently pointed out to me:
“One of the aims of the funding programme was to motivate involvement by people whose skills are less often found in open hardware communities (like professional design engineers etc) but there is no restriction on whether or not they have worked on open projects before.”
Best!
Nico