Although hotspots can be placed anywhere and network coverage created, there are nuances with establishing trust in a new area. This is to prevent what the whitepaper calls “alternate reality attacks”. A trust “anchor” (hotspot) that provides coverage needs to initially be verified whether it’s through voting, trusted deployments, etc. Once a known good anchor has been established the network can grow from there.
Having said that, any hotspot can still participate in routing data from machines, but if you are in a geographical region without any trust anchors you would be excluded from participating in the consensus group. You still gain in score for helping to verify others, but it’s unlikely you’d be one of the highest scoring miners on the network.