The Falcons made some pretty big headlines when they cut Grady Jackson, who has since taken his enormous self to Jacksonville's defensive line. With little to no depth behind Trey Lewis besides the recently injured Montavius Stanley, the team inevitably had to make some kind of move.
Trey Lewis isn't likely to feel this guy breathing down his neck, but he's a reasonably big tackle who had some success in the same role in Buffalo. The key mention in the ESPN article is that Anderson's good against the run. Trey represents and unknown quantity, so if he's not ready to go against elite backs then it might be a wise idea to let Anderson play. Still, I think the coaching staff is committed to Trey.
This is the kind of signing that I can't complain about at all, though. Tim Anderson has some experience, he's still young and he fills a backup spot where he's needed. This was a no-brainer.