It seems to leave the problem of booting the linux installer, which is easy to do from grub.efi - if it is blessed.
At present we install grub.efi manually, using only grub-mkimage to build grub.efi, without using other grub utilities, and mostly just use preloaded modules.
Here is some more info for the intel mac -
Further checking shows that Apple EFI will detect and boot an unblessed file named boot.efi but only if the enclosing folder is blessed.
Will not boot unblessed grub.efi in the same folder.
im81:~ pxw$ bless --info /Volumes/hfsp
finderinfo[0]: 7891 => Blessed System Folder is /Volumes/hfsp/efi/test
finderinfo[1]: 0 => No Blessed System File
finderinfo[2]: 0 => Open-folder linked list empty
finderinfo[3]: 0 => No OS 9 + X blessed 9 folder
finderinfo[4]: 0 => Unused field unset
finderinfo[5]: 7891 => OS X blessed folder is /Volumes/hfsp/efi/test
64-bit VSDB volume id: 0x0F87F7680B9C5211
im81:~ pxw$ ls /Volumes/hfsp/efi/test
boot.efi grub.cfg grub523.efi grub523.icns grub64.icns
im81:~ pxw$
That boots boot.efi using the Option key.
For OSX boot.efi -
im81:~ pxw$ bless --info /
finderinfo[0]: 149 => Blessed System Folder is /System/Library/CoreServices
finderinfo[1]: 297081 => Blessed System File is /System/Library/CoreServices/boot.efi
finderinfo[2]: 0 => Open-folder linked list empty
finderinfo[3]: 0 => No OS 9 + X blessed 9 folder
finderinfo[4]: 0 => Unused field unset
finderinfo[5]: 149 => OS X blessed folder is /System/Library/CoreServices
64-bit VSDB volume id: 0x0F8CB2A6A4C456E8