Lync Dialing Rule Optimizer
https://www.lyncoptimizer.com/

C:\Program Files\Microsoft Office Communications Server 2007 R2\Mediation Server\MediationServerSvc.exe.config

http://support.microsoft.com/kb/952785

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
                 <appSettings>
                                <add key="RemovePlusFromRequestURI" value="Yes" />
                 </appSettings>
</configuration>

For R2 please read the following article:
http://blogs.technet.com/b/ucspotting/archive/2009/02/28/removeplusfromrequesturi-or-how-to-make-ocs-non-rfc-3966-compliant.aspx