Assuming that apt-get left the msttcorefonts package in a hold state (pending configuration) here are the steps to install the MS corefonts from a local directory.
1. In a terminal or vt, confirm that msttcorefonts is partially installed
$ dpkg -C
If it's listed as broken or hold, then proceed to step two. If it isn't, the grab the msttcorefonts_2.2_all.deb package from a Ubuntu archive and install it manually on the isolated machine.
$ sudo dpkg -i msttcorefont_2.2_all.deb
2. copy the ms corefonts self-extracting cab files into a local directory on the machine you want them installed on. Do not extract the cab files and be sure that you have all of them. You can find a list in /var/lib/dpkg/info/msttcorefonts.postinst (arial32.exe, andale32.exe, etc.)
3. Open the /var/lib/dpkg/info/msttcorefonts.postinst script for editing and change a line at the top of the file that reads "LOCALCOPY=$RET" to "LOCALCOPY=/directorypath/where/you/stored/thefont/cabs
Save the file.
4. Configure the msttcorefont with dpkg
$ sudo dpkg --configure msttcorefonts
If you specified the right directory to where you copied the font self-extracting cab files in the msttcorefonts.postinst script, then msttcorefonts config will output the status of extracting and installing the fonts.