How to execute tasks conditionally using the maven-antrun-plugin?

I need to execute some ant commands depending on an environment variable passed in as a parameter to the maven build command.

At the moment I have 3 tasks blocks and only the tasks block with no condition is being executed.

<tasks name="isProdCheck">
  <condition property="isProd">
    <equals arg1="${environment}" arg2="PROD" />
  </condition>
</tasks>

<tasks if="isProd" depends="isProdCheck">
...
</tasks>

<tasks>
... I am the only block executed
</tasks>

What am I doing wrong, is there a better way to do this?