Are student evaluations of teaching assistants read by others in the faculty? Are student evaluations of teaching assistants read by faculty who assigns teaching duties to TAs or by the primary instructor of the course for which the TA is assisting? 

I recently met the professor whom I was assisting and he said: "...and you got good evaluations last semester...". I was not expecting that.
You should expect that your teaching evaluations will be available to any faculty members in the department.  The lecturer for the class will certainly have access (and this is important for you, if you subsequently look for an academic position; your evaluations will help them to write you a letter of recommendation addressing your teaching).  Other faculty members may also see the evaluations.  In my department, any professor who wanted to see a grad student's teaching evaluations could get them.  Most faculty members are not going to be interested, but whoever makes the teaching assignments may well review your scores.  Other people may also look at your scores, for various reasons; for many years I reviewed all the grad students' teaching evaluations in my department, to look for evidence of any systematic problems.