I am realizing now that in IT sector scope, time, cost are not real constraints for a project manager, their major and real constraint is resource/s. In majority cases I have observed that your project cross limits of scope time cost, when you have issue/s with resource/s and not with process (scope) or schedule (time) and the allotted funds/reserves. In civil projects, being sole owner; PM is all time buried under these constraints along with resource constraint.
In IT situation is different. Mostly in all cases project manager is well aware of scope-time-cost. They keep sponsor/s or the client well in loop about changing situation/s, put queries or doubts whatever they may have/had. In other words, for a PM it is not a constraint, but it is constraint for the organization (or you may call it a tension for sponsor!). What I observe in IT or KPOs the real constraint is resource. verified resource>domain expert resource>subject matter expert or required software, tools and technics expertise.