Ah, if it's the entire dictionary and not filtered by the clients to just those fields, then presumably additional data may be shoved in—specifically the trackers to contact.
No, look at the content of the dictionary: trackers are not part of the "info" dict, so you can add all the trackers you want, it won't change the identity of the torrent. Identity is defined by the infohash.
Trackers are added in the magnet link by adding parameters to the URI: see http://bittorrent.org/beps/bep_0009.html