Pretty much any HDMI switch can be controlled by élan that is designed by companies who are not selling their own control systems.
I'm not sure you're going to find an IP controllable HDMI switch, simply because most companies providing video switches still use RS232 & IR.
If it must be IP ( which I'm not sure why it would have to be) and you are just in love with your Élan system, we can derive a custom solution using Crestron for sure however depending on your current Élan investment, it could be questionable if the cost of this type of creative programming would be worth it vs simply selling off your Élan system and replacing it with Crestron or Savant ( of which these guys build a far superior HDMI product to anyone else currently offering solutions).
All that said, if you have an Élan system that you don't want to part with, just buy an HDMI switch that's RS232 or IR based and call it a day.
If you need recommendations, 1st thing I need to know is how many inputs, how many outputs, and how all your TVs are wired... Meaning what kind of wire and if it goes back to a location where the HDMI switch would go.
I don't subscribe to threads... Just too much email to read but if you want some more info, send me answers to the questions I have via private message, email from my web site or Facebook page...