Yes. I'd do it with Qt's QApplication object. You'll need a PyQt installation of the same version as Scribus' Qt installation.
When I run this as an extension script, it exits Scribus:
import site
# Replace with site.getsitepackages(), site.getusersitepackages()
# from you're system Python installation.
SITE_DIRS = ['C:/Python27', 'C:/Python27/lib/site-packages', ]
for p in SITE_DIRS:
site.addsitedir(p)
import PyQt4.QtGui as gui
app = gui.QApplication.instance()
app.exit(0)