If the chief law enforcement official whose jurisdiction includes the proposed transferee's residence refuses to sign the "law enforcement certification", will the signature of an official in another jurisdiction be acceptable?

No. Effective July 13, 2016, the final rule “Machineguns, Destructive Devices and Certain Other Firearms; Background Checks for Responsible Persons of a Trust or Legal Entity With Respect to Making or Transferring a Firearm” amends the regulations to eliminate the requirement for a certification signed by a CLEO and instead adds a CLEO notification requirement. Prior to the submission of the ATF Form 1 or ATF Form 4 to the Director, all applicants/transferees and responsible persons shall forward a completed copy of ATF Form 1 or Form 4, or a completed copy of Form 5320.23, respectively, to the chief law enforcement officer of the locality in which the applicant or responsible person is located. The chief law enforcement officer is the local chief of police, county sheriff, head of the State police, State or local district attorney or prosecutor.  If the applicant/transferee is not a licensed manufacturer, importer, or dealer qualified under this part and is a partnership, company, association, or corporation, for purposes of this section, it is considered located at its principal office or principal place of business; if the applicant/transferee is not a licensed manufacturer, importer, or dealer qualified under this part and is a trust, for purposes of this section, it is considered located at the primary location at which the firearm will be maintained.

Source ATF: https://www.atf.gov/firearms/qa/if-chief-law-enforcement-official-whose-jurisdiction-includes-proposed-transferees