Hi Jason,
whether or not a call will succeed or not with a 1-direction neighbor relationship depends on how the far end VCS is configured, but with most configurations, this will work. When the far end VCS does not have a corresponding neighbor zone, the call will come in via the DefaultZone rather than the neighbor zone, and it therefore depends if the VCS is configured to accept this specific call.
Unless you have any CPL or search rules which specifically deny calls coming in via the DefaultZone, this should normally work.
Please note that with a 1-way neighbor relationship, you will normally not be able to place calls in the other direction (From the VCS which does not have the corresponding neighbor zone in question) unless you are using DNS to route the call.
Hope this helps,
Andreas