Do studded tires make less than ideal railroad crossings worse?
I think you'll be fine. You might experience some slip, but not enough to cause you to come off the bike or get stuck, etc. 

Three reasons I'll think you'll be alright:


Your tires are also made of rubber, not just metal studs and will deform while on/around the rail. This means that some portion of the rubber tire will be contacting the rail and providing grip.
If you have any speed at all your tire will cross the rail quickly and not spend much time trying to grip it.
The odds of both tires being on the rail at the same time, for any length of time, are pretty low, so the rear tire will be pushing forward or the front will pull enough to get you across it.


Now, there's a small technique that will help you out regardless of conditions and tires: the bunny hop. By lifting even your front tire over the rail, you've eliminated half of your traction problem. Getting the back tire up will pretty much erase the issue all together.