From the debian/changelog in unstable:
asterisk (1:1.2.10.dfsg-3) unstable; urgency=low [ Kilian Krause ] * Add iaxy.bin to asterisk debs to have working IAX support. * asterisk_fix is included on the main asterisk package (Closes: Bug#287025, Bug#360233, Bug#381861)
Appears this was an oversight on the previous package. -- Jamin W. Collins