See the third definition here: http://www.merriam-webster.com/dictionary/vehicle http://www.merriam-webster.com/dictionary/vehicle They're generally referring

See the third definition here: http://www.merriam-webster.com/dictionary/vehicle http://www.merriam-webster.com/dictionary/vehicle They're generally referring to legal entities, investments, and particularly the interplay of a network of the above which exercises various features of countries' tax laws in advantageous ways.