Does the potting soil contain organic matter in want of (further) decomposing?

I'd also like to know how prevalent the bacteria is. But to me the risk of spreading the bacteria would be greater than the small benefit of hanging on to that soil. I've suspected gall on a few potted roses and I threw them out, pot and all. On the other hand maybe your compost pile heats up enough to kill any bacteria. From what I have heard once you see gall the bacteria has spread throughout the plant. But I have heard of cutting out gall and not seeing it anymore. I'd like to ask a plant pathologist who specializes in gall.

Do a web search for crown gall to find out what is involved. Or try using the name Agrobacter tumefasciens.