I have tried to replace t-call-asset with t-call, the result is that each files / lines in the called file are shown as is. So t-call-assets actually group these files listed into a record in ir_attachment, and fetch it at once (I guess to speed up the http). 
Now my issue is, how to have two themes for different pages. (I would like to have afew pages greenish (using css) but not the rest of the website)