We don't know the store date for them. There's no sign of a box art, cartridge, or manual picture.
Don't know if the publisher's website (assuming they have one) lists this game. After all, Capcom Europe doesn't mention having released Mega Man Network Transmission there from what I can tell...
FYI: GBA got quite a few games in Europe that were astoundingly rare, which caused them to not be dumped for ages. Like that one Madagascar version.