Regarding whether bees come out of hives or not during a move:

>From my experience;
When moving hives, bees remain inside if the conditions are cool and the hives well
ventilated - usually early in the season with developing colony sizes.
But later on, when the colony is getting to maximum size, in warm, hot conditions esp. in
thundery periods - the bees hang out in varying degrees - from small patches to extensive
coverage of the hive box. This being more likely if the hive is well stocked with honey
/nectar.

Therefore when moving, the choice is:
a. Leave open, and accept what happens (wandering bees and possible loss and stings) - but
little risk of over heating the colony, or
b. Closing up the entrance with foam, grill or other device (screen) - ensuring ease in
hive movement. This requires that proper ventilation is provided or allowed for - limited
bee wandering problems.

Peter