Nightshade,
I would move them in the fall. Emerald green grow really slow, so for now they should be alright.
They say 4 feet in circumference.
So, if you plant the tree in the hole, imagine a four feet circle all around it in every direction.
Do you know what I mean?
So when you transplant them, which you have to do if it is only 30 inches to the fence, when you dig one out, move it 4 feet from the fence, and 4 feet in every direction.
From the base of the trunk of the arborvitae.
That is your starting point.
Oh, and mulch real good, they aren't established yet.

Someday you will need to paint/stain/wash/replace that fence.
Leave room to work.

And it's not as if they will magically stop growing when they reach a certain size.

I think a previous poster meant a 4' diameter (spread), not circumference :-) At any rate, a 4' spread means the plant only grows approximately 24" in any given direction so you should be OK for the time being. Personally, I would not have the slightest concern about these planted at that distance and leaving them in place is far better than the trauma of moving them. And these plants can be sheared as well to keep them to a more narrow or hedge-like profile.

FWIW, plants DO slow growth dramatically once they reach their genetic potential, provided they are not overstimulated with water and fertilization. One of the better features of the tree in question is its extremely uniform growth habit and growth rate - 12-15' tall and 3-4' wide. Yes, it can get bigger but typically not routinely and if it does, it will do so very slowly.