It's not clear whether lane placement affects results, but it's true that the middle lanes are often favored, and qualification systems tend to place better-performing swimmers towards the middle. Here's two non-professional discussions on the matter:
[1] https://www.quora.com/In-competitive-swimming-why-are-the-in...
[2] http://sports.stackexchange.com/questions/1326/in-swimming-i...