The mechanism Gollwitzer proposes is that presenting your plans to others make them a "social reality", which tricks your brain into feeling like you've already completed some steps towards that goal even though you haven''t.
This means this is mostly relevant to tasks whose main goal is to define yourself both in your eyes and in those of others, ie. goals of the form "I want to lose weight", "I want to start a company", "I want to write a book". In these cases, the simple fact of announcing these goals will portray you in as someone who's interested in being fit, an entrepreneur, or a writer -- if you've already convinced yourself and your friends that you're an artist in spirit, why bother going through the pain of actually writing that book? Because in these types of goals you are the one who decides whether you've been successful or not, the fact this social reality already makes you feel like you've accomplished something means you're less likely to judge yourself harshly for not actually following through.
However for goals like "I'm going to deliver XYZ this quarter" the cost of failing to deliver on your promises is potentially much greater than the social benefit you get from looking like the ambitious worker that makes big promises, because the condition of success doesn't depend solely on what you feel, but on the judgement of others. So it's likely that in the workplace the traditional recommendation of making goals explicit is still the way to go in most cases. Note though it's all a matter of incentives: if you derive enjoyment from being the one who underpromises and overdelivers, then the benefit you get from positively surprising your colleagues/superiors/customers might prove a stronger motivation than this last mechanism.
On another note, you shouldn't solely base your decision to announce your goals on this effect: one must also take into account the other benefits of making their goals public, opportunities for emulation, counsel/support, connecting with individuals with similar goals, etc. Often these benefits will far outweigh any potential negative impact on commitment (which can be fairly minor).
PS: While reading up on Gollwitzer's research I found this other tidbit some might find interesting: goals formulated in the form of an "if-then" plan (ie. with an implementation intention) tend to have a higher attainment rate than those that are more abstract [1]