There's always only one at the highest level of quality at a fine-grained enough resolution.
Whether there's only one at sufficient quality for use, and if it is possible to switch between them in realtime without problems caused by the switch (e.g., data locked up in the provider that is down) is the relevant question, and whether the cost of building the multi-provider switching capability is worth it given the cost vs. risk of outage. All those are complicated questions that are application specific, not ones that have an easy answer on a global, uniform basis.
