Tango to Eagle Schematic import
Is Tango open source? Is their format documented? If so, Eagle has a scripting language, depending on how many schematics you have, it might be worth spending the time learning the scripting language and writing a tool to import it.

You should also ask on the Eagle newsgroups, it's on usenet which is kind of obscure, but you can use Mozilla Thunderbird to read/post to them.