There is a slight difference in the thickness of the rail at the at the base and web, but not at the rail head.
Ed Rappe
The track gauge (width between the rails) is the most important thing to consider. If both are 1.25 inches (O Scale), then both will be compatible with your equipment.
Joining the two types together may require more work than using only one brand. When I look at Atlas, the railheads look wider than other brands. Since I am used to seeing the other brands, in my mind the atlas looks wrong. But that is not the issue here.
If the Atlas rail is indeed wider over all, the same rail joiners may not just snap in place. However if you follow the recommended guidelines for DCC and put drops on every piece of rail, you can have loose fits on the rail joiners.
As someone who makes and sells track gauges to people who are hand laying track, I can without a doubt confirm, Atlas code 148 rail DOES have a wider head than ME rail. While it is slight, one of my gauges made for code 148 rail, may NOT on occasion fit on a piece of Atlas rail, as they are machined to fit ME rail. With that said, you should have no problem joining the two or operating across that joint, as the difference in rail head width is only about 0.005".
