Assigning a keyboard shortcut to Trash is a waste of available shortcut
especially when this shortcut is single-modifier Win+T, and cannot be overriden
Seriously, whoever came up with that idea obviously didn't think it through. I mean, i understand that everything in the Unity panel should be accessible by keyboard; but keeping this in mind, i would question the decision to place Trash in there at all. I don't know what kind of users you are working with, but i have never in my life seen anyone use trash so frequently that they would benefit from having a keyboard shortcut for it.
On the other hand, there are many perfectly good uses of Win+T keyboard combination for power users, such as "open (T)erminal"
If it is really necessary to see Trash all the time (which i doubt, but i'll admit that i have no usability testing backing that opinion), perhaps placing it on the indicator applet would be a better idea