Not really. All the units that can attack a sub, they attack as normal. The defending sub can only attack after the first round of attack. If you have any questions on the ruling, you can download the rules from www.avalonhill.com
To let the Allies shere IPC income, will destroy the game for sure, and is a madman idea.
Well, that’s the way I played until the other day. When my friend taught me the rules he honestly thought the allies could share funds. I finally questioned it on Friday after he bought 5 fighters and six tanks for the Soviet Union. Apparently, either he and his dad glanced at the rules about allied soldiers being turned into Soviets when in a Russian province and thought sharing of IPCs was allowed, or his dad just pulled a fast one on him. (The first time my friend played he was Germany.) However, before that point we had never used that rule to its fullest extent, since we normally had another player and no one wants to give all their income away.