Multisite and custom taxonomy… quid ?

In multisite context and WordPress version 4.2.2, with this function in blog_id #3:

switch_to_blog( 2 );

have we really switched in blog_id #2 to fire a query (new WP_Query ( $query ) ;) including a custom taxonomy here (‘domain’) ?

In fact NO, because interpreting $query needs the taxonomy to be declared in blog_id #3 where this code is.
A workaround ?
The plugin registering this new taxonomy must not be ‘network activated’ but one by one in #2 and #3 and in properties of this taxonomy, define where the taxonomy must be visible (here #2)
'show_ui' => ($current_blog->blog_id == 2 ) ? true :false,

With this workaround, the deficiency of switch_to_blog( 2 ); is “fixed” and it now possible to display with a custom function (including complex query) in theme of website #3 a list of posts coming from #2.