SO…it seems that you can't localize the values in the share properties file, but I had to add a properties file into the REPO section of my amp. I added it my amp's service-context.xml file AND (the most annoying part) you don't refer to it as .properties, but you just give the basename (different from the "models" property where you DO give the extension).
So below the code where I specify my model file I added:
<property name="labels">
<list>
<value>alfresco/module/${project.artifactId}/messages/myModel</value>
</list>
</property>