Most employees are usually allowed some small pockets of free time, that they may use to read something related to Buddhism. That's fine. Most people use such legitimate small pockets of free time to look at social media, or text their family and friends outside of work.
However, browsing Dhamma or social media during the time they are supposed to be working is a kind of stealing - taking something that is not given to them. Employees have contractually given up a lot of their time and effort to their employer in exchange for remuneration. So, not giving one's time and effort as promised is a kind of stealing.
Stealing of course violates one of the five precepts, but I won't put browsing Dhamma during working time in a full time employment, in the same category as stealing the little money that a poor family has, to feed themselves.
What kind of effect would it have? Well, employees may get fired and lose their source of income. They would also lose their reputation.
I think this is a good example of the practice of heedfulness (appamada). We should be ever heedful and mindful of our duties and responsibilities, as well as the five precepts. It's true that one may not be able to fulfill the five precepts perfectly, but at least one should try his or her best.
Talking about fulfilling the precepts perfectly, this answer about stealing a sniff of the scent of flowers (from SN 9.14) is very apt for this case. Using the legitimate small pockets of free time during working time to read the Dhamma is like stealing a sniff of the scent of flowers. Those aiming for perfection in virtue (paramita or parami) should avoid it. But then again, those aiming for perfection in virtue may be better suited to the monastic life than the lay life.