As I see it your problem has already solved. The city has planted what will become a complete and total screen from the road. All you have to do is wait for it to grow. Which won't be that long actually. Cities have a way of planting trees and then ignoring that they need water. If your city does this, you could supplement the water so that the trees live and grow faster. As you have a wooded area next to the new blue spruce screen, it's possible that it may produce shade on the new plants. If this happens, they're not going to like it and that side of the screen (that faces you) may become thin of foliage and not look all that great. If it was me, I would be appreciate the new screen to much that I would remove any of my saplings that caused conflict with light. Only the ones that caused conflict. In the end, looking through your woods to that nice backdrop could be quite a pleasing picture.

Not sure of how you envision adding in "a variety of trees / bushes / shrubs / grasses," but if it was me, I would want to maximize my view INTO the woods to that nice new backdrop (that I know some day will come) instead of filling the woods with a clutter of various plants, some of which will end up not looking all that great because of the shade of the woods. What the wooded area could benefit by is a groundcover that unifies the whole area. It could be allowed to spread all the way to the backdrop (which I notice since it in only mulch will at some point become bare. The city is going to give up on mulching what to them is the back side.) I'm not saying there couldn't be some shrubs at the back side of the woods, but where and what they are should be approached strategically. Not just filling it up. There is no need for anything at the foreground of this area but groundcover.

BTW, excellent job on providing photographs. Wish everyone would be so thoughtful.

Realize that in five years or so you will have a wall of dark green. Whatever you plant should not shade out the spruces and should look good against the dark green backdrop. I would plant some small dogwoods well away from the spruces, realizing that they, (the spruces), will get 20-40 ft. tall and perhaps 20ft spread. Flowering shrubs will look nice back there, and will also grow fast. A beautiful flowering groundcover will also accent the evergreens. The standards are lamium, vinca/periwinkle but I also grew sweet woodruff which has lovely white flowers, and ajuga comes in a multitude of flower and foliage colors.

You could plant additional blue spruces (or a complementary conifer), offsetting them from the existing row. Plant them inside your yard but in the visual space between each spruce -- you'll create a zigzag of trees that will give the appearance of a solid line sooner while maintaining proper spacing.