Debian no longer rebrands Firefox as Iceweasel even in oldstable Wheezy. If you modify your base SCE list with firefox-esr and remove iceweasel reference, then re-import rather than update it's still a problem? Jason will know, not sure the SCE scripts determine transitional just dependencies. In the rare event a package becomes transitional, maybe just a manual re-import is the easiest fix? Update checked a dCore-jessie system and yes it wants to update Iceweasel with both iceweasel and firefox-esr.
Edit: Just ran sce-update and Iceweasel is now Firefox-esr. Rebooted and update check did not flag an update but that's because there was no DEBINX change. Still calleded Iceweasel as the package name in ondemand and in the menu. Can be launched as iceweasel, firefox or firefox-esr. I do not use a list file, just a dependency on Xorg. Running dCore-jessie if this helps.