Arriva pulled the 'Veganuary' ads from its buses in the county before Christmas after they were objected to.
The operator cited errors in the approval process of its third-party supplier as the reason behind the decision, and denied it had anything to do with the content.
But the company has now replaced the posters, saying the issue had been resolved.
'Veganuary' adverts were placed on 20 Arriva buses in the county in December, designed by the national Veganuary campaign which encourages people to go without animal products for the first month of the year.
The Shropshire Veggies and Vegans group, which fundraised all year to pay for the adverts, said Arriva's decision to remove them was "totally unjustified" and encouraged supporters to make their views known to the company.
The national Veganuary campaign responded to the decision, saying it was "outrageous".
One of the adverts focused on environmental side of veganism, while another was about the treatment of cows in the dairy industry.
Jo Ruff, from the group, said: "The bus posters were removed after just being up for one week.
"My initial notification came from the organisers on the day they were being removed, giving me no option to challenge the decision. I was told it was due to a number of complaints.
"Many people were disappointed by this and complaints regarding them being removed were huge. They would have far outweighed the unnecessary complaints against us.
"Being reinstated shows how the facts about the horrific cruelty of the meat and dairy industry are very true. It also shows how essential it is to be vegan if we want our planet, and thus ourselves, to survive."
An Arriva spokeswoman said: “Recently, several adverts on our buses in Shropshire relating to the GoVegan campaign were removed due to an operational error which has now been resolved.
"Arriva is and continues to remain impartial to the content of these adverts and can confirm that these have been reinstated as agreed between the advertiser and our third-party supplier."
It was the second year in a row that a row had broken out over the adverts, but the first time they had actually been removed. Last winter Shropshire Council’s deputy leader Steve Charmley criticised Arriva for running the adverts in a county with so many livestock and dairy farms.