Unfortunately, you do not get to keep the locality portion of your salary when you move to a different facility. With the 50% on the go and 50% upon certification, you will probably be taking a pay cut when you first move.
Per the Slate Book
All of the transfer pay section is in terms of Basic Pay, which the slate book defines as...
c. Basic Pay: Employee’s pay rate excluding applicable Locality Pay adjustment in effect.
Ex. (No locality and bottom of the band)
Level 6 - $62,914
Level 9 - $84,884
84,884-62,914 = $21,970
50% 0f $21,970 = $10,985
New salary without locality on the go = $62,914+$10,985 = $73,889
$73,889*MSY's rest of US Locality of 15.06% = $85,028 on the go
then $97,668 upon certification.
The numbers will vary slightly based on how long you've been in the agency, but in terms of take home pay you basically get screwed. Advancing your career up 3 levels with little to no difference in pay, but hey you do get off of Long Island, which is borderline priceless in my book.