Try this :
<?xml version="1.0" encoding="UTF-8"?>
<mule xmlns="http://www.mulesoft.org/schema/mule/core"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:spring="http://www.springframework.org/schema/beans"
xsi:schemaLocation="
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.mulesoft.org/schema/mule/core http://www.mulesoft.org/schema/mule/core/3.2/mule.xsd">
<spring:beans>
<spring:bean id="initializer" class="org.myclass.that.implements.muleContextNotificationListener.MuleContextNotification"/>
</spring:beans>
<notifications>
<notification event="CONTEXT"/>
<notification-listener ref="initializer"/>
</notifications>
</mule>
(Inspired on this)