In order to package plexus-utils into sonar-plugin following code snippet can be used:
<dependency>
<groupId>org.codehaus.sonar</groupId>
<artifactId>sonar-plugin-api</artifactId>
<version>${sonar.version}</version>
<exclusions>
<exclusion>
<groupId>org.codehaus.plexus</groupId>
<artifactId>plexus-utils</artifactId>
</exclusion>
</exclusions>
</dependency>
<dependency>
<groupId>org.codehaus.plexus</groupId>
<artifactId>plexus-utils</artifactId>
<version>1.5.6</version>
</dependency>
Same technique can be used to replace any dependency provided by sonar-plugin-api. And plugin can use those dependencies - see SONAR-1862.
Integration test for such case added in r5671.
I've attached integration test - can be placed into subprojects/sonar-update-center/sonar-packaging-maven-plugin/src/it