There are several considerations beside the
voltage: Most (if not all) European power is
50 Hz, versus 60 Hz in the USA; The legally
allotted frequency for X10 RF signals differs
between the USA and Europe; Power line plugs
and recepticles are different for the
different countries.
So the short answer to your question is No.
There are a variety of X10 products designed
for the European market, however I don't
believe a European version of the ActiveHome
Pro CM15A has yet been released. See:
http://www.x10europe.com