Spike may not be quite aware of it, but he's probably the person whose opinion Jack values the most on judging others in the dome. They may not always see eye to eye but a lot of that seems to be because they see things so differently - Spike sees what he doesn't, comes at things from a different angle, and he's beginning to realise that rather than arguing with it, he might be able to use that different viewpoint to help understand what he's too old and set in his ways to get.
So while he still doesn't really get exactly where Tyki's coming from, he does accept that Spike knows what he's talking about here.
"What's happening tonight?" he asks, frowning slightly.