First, let's not use tobiano and "pinto" interchangably as there are four different pinto patterns - Tobiano, Frame, Splash, and Sabino.
The chances of breeding two minimal expression (only leg white) Tobianos to each other is not high even in Miniatures where the rate of minimal expression Tobianos is much higher than it is in big horses. If you do breed to minimals to each other though you could produce a homozygous Tobiano BUT I know of no instance where a homozygous Tobiano individual is minimally marked. Second row of get, 4th foal at this link
http://bellevuefarm.com/Mares%20Pedigrees/queen.htm is a classic example of a minimal expression Tobiano (the dam is tested to be homozygous Tobiano).
Tobiano is not the only pattern that can be homozygous. Splash White can also be homozygous but one copy of Splash (heterozygous) does not always create pinto patterned individuals. Some heterozygous Splash individuals may only have a large snip, a little bit of leg white, or a blue eye.
One of the Sabino genes (there are many), Sb1, can also be homozygous. Homozygous Sb1 will usually produce a nearly completely white individual. This Missouri Foxtrotter stallion is an example of a homozygous Sb1 individual -
http://www.mikarmafarm.com/stud.html Sb1 when heterozygous can be very minimal or very highly expressed. This mare is a minimally marked heterozygous Sb1
http://www.platteridgefarm.com/libbyped.html where her sire (2nd stallion down on this page)
http://www.platteridgefarm.com/stud.html is a very highly expressed heterozygous Sb1 as is her foal from this year (8th photo down on this page)
http://www.platteridgefarm.com/foal.html
The only pinto pattern that absolutely cannot be homozygous is Frame. Frame when homozygous produces a lethal white overo foal that is not viable due to an incomplete digestive system.