Yep, it's possible. Like redd said, if the event was one of their weak events then it's easier. Another thing to consider is gender. Walkons count towards the athlete participation count for Title IX so it's probably harder for a guy to walkon than a girl.
I used to have a copy of the A&M walkon standards but there's a copy of the FSU track standards out there and those times should be similar to A&M's; the times aren't always set in stone - they're just a helpful guideline. As redd said, email the coaches and fill out the prospective student athlete questionnaire on the Aggie Athletics website.