In Maven you can define properties using environment variables, e.g.:
<someProp>${env.SOME_ENV}<someProp>
See also: http://books.sonatype.com/mvnref-book/reference/resource-filtering-sect-properties.html

On the command line, those placeholders a replaced as expected. This can be checked via mvn help:effective-pom.

Unfortunately, ParsedPomFile.getProperties() does not replace those placeholders. It returns them "as is" (e.g. "${env.SOME_ENV}").