It will be on Origin, and you can join game through the friends window at the very least. Plus it has dedicated servers, so you can all join the same server easily. I can't imagine this will be an issue.
A party system should be pretty standard in this day and age. However, after Battlefield 4 launched without one (and still doesn't have one) I'm just a tad wary that there might not be one. Not comparing BF4 to TF, but now I have to never assume that every modern game will ship with a party system.
They talked about being both a single player and within your "party". I hope this is the case. Its why I have asked so many to be on my friends list on Origin. I don't never not ain't ever gonna play alone! At least if I can help it!
I hope they will allows us to easily play with friends. I know that Origin is a very nice platform when joining and inviting friends so hopefully this will be implemented. -- Vez