Yes - however, at the moment it's a case of dpkg -x somepkg.deb /var/lib/install (and for all the required dependencies). This could be optimised, however, by install apt and configuring packages which are already present in the device (e.g. libc6 etc.)

I've used this to install Perl, screen (including its dependent ncurses) and a few other command line bits & bobs without recompiling them in Scratchbox.

If you've got root access, you can change /var/lib/install to just / and avoid any problems with config files etc. (no pun intended)