The work, which includes a billboard made of a fake trillion dollars saying "Thanks to Mugabe this money is wallpaper", attacked President Robert Mugabe and his government for trying to close the newspaper.
Akira Kagami, the president of the jury and the executive officer, global and executive creative director at Dentsu, said: "Outdoor is not just a category but is a way of bringing about social change, which is what this campaign does."
The UK managed to bag five awards in total but failed to pick up any golds.
Abbott Mead Vickers BBDO and DDB grabbed a silver apiece for "inner child" for the Museum of Childhood and "global downturn" for the Financial Times, respectively.
DDB also picked up three bronze Lions for its work for the Harvey Nichols Bristol store opening.
KS Chax, a juror and the national creative director of DraftFCB and Ulka Mumbai, said: "Silver winners are about identifying what you want to say then doing it simply and effectively, but the gold award needs to offer a bit more, a bit extra."
The main debate was around the future of outdoor and the emergence of media such as ambient, with specific mention going to "in the streets" campaign to promote the launch of Oasis' Dig Out Your Soul by Bartle Bogle Hegarty New York.
Rob Belgiovane, a juror and partner, executive creative director of BWM Melbourne, said: "Ambient and new outdoor media, such as ‘in the streets', are where the category is going, and it feels like this is going to be the last time a traditional outdoor campaign picks up the Grand Prix."
More from Cannes Lions 2009