Opinions on Glass Shelves

No idea about cracked glass but generally you not going to get the best from glass

toss the glass, and head to your local granite counter top guy. Will cost you about 125 per shelf for real granite.
Much more dead than any kind of glass and much more rigid than glass.

This doesn't sound like your average glass shelf. There is not much info on the Billy Bag's site but they do refer to 1" thick glass shelves. I'm guessing that the cracked glass provides a very large number of random surfaces to break up/slow down any vibrations. Sounds like a good question to ask the factory. Don't just take the salesman's explanation. I would move carefully. By going to a more deadened stand you may lose some of what you have now. I can tap on my stand with the stylus down and hear it in my speakers. I know people make a big deal of this, but I'm not convinced that it means anything. If I smack my preamp with a hammer I'm sure I'll hear that through my speakers as well. But what does that really mean?

Some will tell you any glass shelf should be avoided.

Some very highly regarded shelving systems including those from Naim and Wilson Benesch use glass shelves.

Unfortunately you will get people on both sides who are convinced those on the other side are clueless. Sorry to be of no help but the effectiveness of things like shelves, footers, etc. are highly dependent on the equipment they will used with.

Buy used and experiment. Have fun.

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If the shelf is "cracked glass", chances are the shelf is a laminated unit of 3 seperate pieces of glass fused together with a clear rubber-like innerliner. The unit is heated in an autoclave to melt the innerliner and fuse the peices together. The "cracked" part would be a piece of shattered tempered glass in the center position. You could justify that the rubber innerliner could have dampening properties but that alone does not assure a good performance.