The phrasal verb mentioned in the title, wheeled on, can't be found in any* dictionary. Usages:
In fact it was the experts, or at least those wheeled on by the remainers who didn't get it. -- Roger Scruton
Most of the "experts" wheeled on by the Beeb are Scottish. -- Ann Widdecombe
She suspected Daddy had been wheeled on by Letitia to keep her in play, to enable his daughter to concentrate and judge in silence. -- Barbara Anderson, Portrait of the Artist's Wife
From the usages above I guess it is an expressive way of saying "appointed".
If you are familiar with the expression, would you define it and perhaps elaborate on its meaning?
* As @Clare pointed out, it is defined in the Oxford dictionaries.