If Luigi is to win, he's both going to have to find a way to slow down and outsmart Tails.Negative Zone has the former in the bag, and probably the latter considering how it can put people to sleep and make them taunt uncontrollably.
EDIT: Also, it's mentioned in Tails' Sonic Jam bio that he has a phobia of thunder.
The thunder phobia shouldn't affect Tails any harder then Luigi's in-general cowardice though. There has to be levels in Sonic that there was thunder and lightning in the background but Tails was having no problem. (I think the final level of Sonic Heroes Final Fortress had a storm in the background). Though electricity powers is different from storm thunder.
I feel it's a bit of a cop-out if Luigi wins just by Negative Zone. Considering Negative Zone doesn't cover a huge area, and doesn't even last that long. Tails will struggle against it still. But if Luigi wins using it, it just feels a bit contrived.
I wonder if Luigi will have his poultergust for this fight. Not sure it would help that much. I imagine he'll have all his power ups at his disposal.
Unless Tails is a ghost (Which well of course Luigi will have won then because Tails would be dead) then yeah the Poltergeist isn't useful to him. Wonder if they should even bother with the power-ups since it'd essentially be the same as the Mario & Sonic battle. Tails even has a Super Form like Sonic does
I wonder if we'll also get the Tornado Vs. Bro-bot from Super Paper Mario. That could be interesting.