To quote one European plate:
"When under radar control departing aircraft shall maintain a speed not exceeding 250kt until crossing FL100.
a) The above speed limit may be requested or removed by ATC with the phrase "NO ATC RESTRICTION ON SPEED"
b) Pilots unable to comply with such a limitation shall inform ATC when requesting startup clearance."
Lots of places will have local rulings and routings for noise abatement, terrain clearance etc.
The EGNX plate states:
"To ensure accurate spacing, ATC may request specific speeds and pilots are requested to comply with speed adjustments promptly and within their own operational constraints"
Think that sums it up really: ATC can come out with "No Speed" at which point speed control is yours and all you need do is follow the company profile and observe the birdstrike speed for your a/c type.
HTH.