Hmm, perhaps you can come up with some mechanism to emit a JMX notification when the connection pool (i.e. the standby db) is available. Then add a barrier (http://wiki.jboss.org/wiki/BarrierController). Then the JMS services depend on the barrier.
Very convoluted. And when the node becomes master, you'll get noise in the logs as complaining about unsatisfied dependencies. But then as the barrier gets deployed, the dependencies will be satisfied and the JMS server will start.
Another possible direction is to use a custom subclass of HASingletonController that overrides startSingleton() and blocks at the beginning waiting for the connection pool to become available before continuing. Again, you need some sort of signal that the pool is available.