Yes, with the exception of hapiness (and I'm not sure about CS influence since GnK), all bonuses are additive, including Swedens GP generation ability and its interaction with other things such as National epic, garden, fredom opener and Leaning Tower.
In terms of GP generation power however, the fact that they get more expensive over time (think area of a right angle triangle) means it follows a very approximate square root relationship, reducing the UA power. Also what you really care about is turns per great person, not GP points, so you really care about the reciprocal. Thus if you've gone for all the GP generation buffs, Swedens UA isn't actually adding much to it at all in terms of extra GP because of it.
Example - say you have a lot of DoF's, like 5. Say you also have all 4 of the other GP generation buffs (+100%). Thats a total of +150%. For simplicity say you only work one type of specialist in one city, and over the course of the game generate 4000 points - that's equivalent to 8 great people. now the extra 100% (which any civ can do) gives 8000 points, or 12 great people - an extra 4 people. With the Sweden UA, that's 10000 points, or 13 great people - only 1 extra person! Now lets look at buildtimes. The 8th gp takes 800 points. say you have a base of 12 points per turn. For the regular player thats 67 turns. For the regular player with buffs, that's 24 per turn, a total of 34 turns, a saving of 33 turns - but sweden will not save an extra half of that (16 or 17). They'll have 30 gpppt, taking 27 turns, a saving of only 7 turns.
Needless to say, if you can't get that many DoFs, it tails off further still.