Pokemon Center Wireless
Original source page mentioned "it's the last day for Mystic and Eon Ticket redemption", so I'm guessing that this image is related to that. The pamphlet shown on the original source page also appears to correspond to the snippet of it shown in the GBA + wireless image, so they've been combined.
Note: Only the Mystic Ticket was distributed via Wireless. Eon Ticket was via Link Cable.
http://web.archive.org/web/20070114111635/http://www.pokemon.co.jp/special/ticket/
Source: http://pikachuftt.blog82.fc2.com/blog-entry-63.html?sp