Eddie Bauer makes a 15deg bag with Pertex Quantum shell and Apex insulation. I had never considered EB for bags until I stumbled upon them last week. I have never owned one, just found them online as another option for people. My main bag is a Brooks-Range Drift 15 down bag. I am in the same situation as you, would really like to supplement my gear with a 0-15deg synthetic bag for certain hunts like Alaska. In my research last year I found that the MH Hyperlamina 0 deg bag was the best warmth/weight ratio for a synthetic. They discontinued that model (I believe) and re-released a new version of the Lamina bags for this year.
With respect to the non-Euro standard rated bags made by a lot of hunting company's:
You can look at the materials used and reverse engineer the expected warmth ratings of the different bags using the clo values of each material and the loft of the insulation. I plotted these out on a chart so see how they would compare with properly rated bags from non-hunting companies. The results were as OENANTHE has described above. I had both down and synthetic bags in my analysis with some companies really rising to the top and some sinking to the bottom. There was one company (backpacking company) whose ratings must have been fabricated. They were claiming a 15 deg bag when the materials used were the same as all of their competitors' 30 deg bags. Other companies are very conservative with their ratings. Western Mountaineering, Kuiu, Brooks-Range all had ratings that were 100% justifiable based on their materials, and maybe even warmer than they were giving themselves credit for.
It is possible that a lot of these hunting bags are warmer than their materials alone would indicate. This could be a function of design, volume/geometry, coatings on the shell material, etc. Having never slept in most of these bags i do not have any first hand knowledge about how "warm" they sleep. But "in general," the hunting company bags are a little heavier and more durable and the ratings are more interpretive since there are no standard ratings.