Liquid water/ammonia mantles are probably quite common - present in every ice moon above ~500 km radius (and maybe one below) - but the energy resources to drive life deep beneath the ice will be limited. Europa and maybe Enceladus seem to have sufficiently vigorous exchange of material between crust and ocean to supply radiation produced oxidisers. What they also need is a vigorous source of reductants - sulfur and methane can plausibly be recycled, after oxidation, through the silicates in the rocky core, and methane can be made into longer chain hydrocarbons in the ice under radiation.