Yes, you can use eZ publish in a failover / redundancy environment. There are several ways of setting up this. You need to use the clustering functionality in MySQL and e.g. Linux Virtual server.
Some information about this is found here: http://ez.no/developer/ez_publish_3/articles/ez_publish_3_enterprise_setup_test
Our environment has failover capabilities. As long as you follow the standard failover rules for hardware, software in our case Linux, Apache and MySQL you will be fine.
Tony
Tony Wood : twitter.com/tonywood
Vision with Technology
Experts in eZ Publish consulting & development