Siteacccesses that include a dash (-) appear to work correctly, but when accessed will not correctly resolve their language lists, and possibly other siteaccess-specific settings.

Example:

Have two siteaccesses, "por" and "por-PT":

ezpublish:
  system:
    por:    { languages: [por-PT, eng-GB] }
    por-PT: { languages: [por-PT, eng-GB] }

(unnecessary details omitted)

When /por is accessed, it is correctly resolved, including translated objects. ezpublish.siteaccess and app.request.locale in Twig templates are "por" and "pt_PT" respectively, as expected.

However, when /por-PT is accessed, ezpublish.siteaccess is, as expected, "por-PT" (so siteaccess matching for siteaccesses with dashes seems to work at least partially), but app.request.locale defaults to "en", and content objects are displayed with the default language, and not the primary siteaccess language.