"Meist in privaten Händen"
My dictionary of choice says, meistens and meist is never most. http://dict.leo.org/?search=meistens
I think, and this is my own interpretation, 'mostly' refers to something abstract like time or times, as in 'in most cases', 'most of the times' or as a synonym for 'in general', while 'most' actually refers to something quantitive, like in my other examples. This is not completely true anyway, since mostly can mean 'größtenteils', too. But I think it's a good rule of the thumb.