Signed consent forms are better. However, the important point is to obtain their consent to transfer the file, so you could document their consent to transfer the file.
Re the custodian, that is correct. You can review the guidelines in the following NSBEP document (URL below). The custodian should be a registrant of the NSBEP.
https://www.ns-rp.ca/downloads/NSBEP_guidelines_for_retirement_planning.pdf
Reference:
Consent forms and Custodian