When I did engineering consultancy, the team was usually thrown together from whoever was available. Usually they knew each other at least a little but it wasn't exactly the same team on each project. But yeah, the team involved in the sale and the team involved in the execution often had very little overlap (though, sometimes it was the B-team selling something unachievable to the customer and then handing it over to the A-team, which has more or less the same effect as far as the client's concerned. The swapping isn't necessarily a deliberate act of subterfuge but more a consequence of how people's time was managed: clients would generally take some time to actually commit and it's not feasible to keep a team on standby for every sales lead).