What steps will reproduce the problem?
1. Configure Essentials to allow of plugins to manage names
2. Configure iCPL ShowInTAB: true
3. Chat TAB complete will not work no matter if a nick is set or default name is set

What is the expected output? What do you see instead?
The expect output would be the ability to simply type U press TAB and complete would put User. Instead nothing happens as it seems to be incompatible.

What version of the product are you using?
Essentials 2.9.2
iChat 2.5.7
iChatPlayerList 0.4

Do you have an error log of what happened?
No error is present, functionality is missing.

Please provide any additional information below.
During my research into the issue I noticed Essentials used to include this in their config:

change-displayname: true This option allows you to completely disable the displayname changing

change-playerlist: true This option enables (tab) player list updates, which updates the list with players displayname (if short enough). This option may cause nickname tab completion to fail.

They've since removed the "This option may cause nickname tab completion to fail." so I'd imagine whatever they did would probably help you out here. I hope this is some help.