I've never used one but have heard that although they cannot actually breach the material, whatever is inside gets thoroughly crushed and ground. You'd probably want to hang it high, assuming trees are available, in which case you can't use the cable to secure it to the tree. You could then expect to have it carried off should it fall into "enemy paws". Been there done that.

I've been biting the bullet and using a hard canister in grizzly country, where most of the time I've been above treeline anyway. On a bike you're unlikely to find yourself in such an environment. On my bike tours I just try to do a good hang with a regular stuff sack.