<<The SID has an intermediate 3000' level off. The engine noise is noted when having retracted the flap and maintaining 250 knots, the controller cancels the restriction and the pilots accelerate at 3000' in a level flight profile.>>
When the controller says "No ATC speed restriction" he is not relieving you of your responsibilities for noise abatement; he has made a tactical decision based on other traffic and such decisions can rarely be made prior to departure in a busy TMA. For example, your rate of turn after take-off might be wider than expected and lead you towards other traffic. In such circumstances it would be foolish to take off the speed restriction and have you make a wider turn.
However... I've stopped plenty of a/c off at altitudes before the final SID altitude and if I had a quid for every such pilot who has said "can we cancel the speed restriction" before I've got in and done it I wouldn't be selling shoelaces to complement my pension!