Here is an example where the jetty-maven-plugin has a dependency on jtidy replaced with a newer version:
<plugin>
<groupId>org.mortbay.jetty</groupId>
<artifactId>jetty-maven-plugin</artifactId>
<dependencies>
<dependency>
<groupId>net.sf.jtidy</groupId>
<artifactId>jtidy</artifactId>
<version>r938</version>
</dependency>
<dependency>
<groupId>org.apache.maven.plugin-tools</groupId>
<artifactId>maven-plugin-tools-api</artifactId>
<version>2.5.1</version>
<exclusions>
<exclusion>
<groupId>jetty</groupId>
<artifactId>jetty</artifactId>
</exclusion>
</exclusions>
</dependency>
</dependencies>
[...]
</plugin>