Currently I use the "Export a Scout Project" wizard to deploy an application to tomcat8. Is it possible to export an eclipse scout project from the command line?
This depends on your Scout version: 5.1 and newer use a plain maven build which generates a war file. This can be invoked from command line using mvn install on the parent pom of your project. See http://tools.bsi-software.com/scoutbook/5.2/latest/book_scout_intro/scout_intro/scout_intro.html#sec-helloworld_export for more details. Please note that this version is not released officially yet and will be part of the Eclipse Neon release in 2016-06-22.
Versions before 5.1 are based on the PDE product export mechanism. This exports a *.product file as if you click on the "Eclipse Product export wizard" link in the product editor. This can also be executed from command line using a headless eclipse: http://help.eclipse.org/juno/topic/org.eclipse.pde.doc.user/tasks/pde_product_build.htm?cp=4_2_0_0. However you may need to post process the exported war files manually and add artifacts like the equinox servlet bridge, web.xml and launch.ini files. Alternatively you can also setup a maven+tycho build as already mentioned by Jmini.