Hi,
titles says it all. ATC is not aware of terrain at all. That is particular important for missions where you get penalized for flying the way you think it is right.Just had a VIP flight mission in the alps. Apart from the deadly desend instructions, you can often not apply the teardrop VFR pattern entry or any other VFR entry pattern. Many airports have specific STARs and approaches to take terrain into account.
Best regards