Many have asked me, “Does ECL support BluePrinting”? My reply is always a solid yes, but (yes there is a but), I should really reply with a question: “Does your external system support BluePrinting”?
Since it is nice that ECL supports BluePrinting, but ECL just exposes items from your external system in SDL Tridion. So for them to be BluePrinted, you should have your ECL Provider make the connection between an SDL Tridion Publication and the specific items you want to show in that context. An ECL item URI contains a Publication URI, so to implement BluePrinting correctly in your provider, you will need to give the child item, the same ECL Item ID as its parent item. The only thing that is tricky there is localization, an ECL item doesn’t really have a localized state, the ECL stub Component can have that state though.