The plastic is so thin that temperatures needed for sterilization would melt or warp it, and then you would not have a usable liner, so forget high-temperature sterilization. It isn't an option.
I guess the deal is this: I wash and re-use the bottles I pump into, so why not the liners my baby drinks out of? Well, in my view, because the liners are more difficult to get clean, because they are wrinkly and the plastic is thin. Even very hot water can warp them, and then you've damaged the integrity of the liner and you risk chemical leakage. The other thing is that I pump into the bottles, put the cap on them, and that's it. They aren't opened until they are dumped into a bottle, and then they are washed and used again. But your baby drinks from that bottle, and bacteria from your baby's mouth gets back into the bottle, and may stay on the plastic through a washing.
If the bottle was emptied and immediately refilled you probably would be fine, I think, but if it sat at all I don't think it's worth the trouble, and not worth the risk either. Seriously, it's like $4.99 for 100 of them at Publix, which is a nickel each. I'm pumping twice a day when at work and getting about 12-16 oz, which is about typical, I think. So between 15 and 20 cents a day. Is the cost really worth it?