In the early days of his business career, Montoto sold clothing and watches in the city of Paso de los Libres. In partnership with Spanish entrepreneurs, he founded Background, a firm that rented offices in Maipú by the hour. The enterprise was not successful, however. He later joined other Spanish partners in establishing a firm that hooked up homes for natural gas.
Metropolitano Montoto went on to be the president of Metropolitano, a
railway consortium. During Montoto's tenure in this position, the General Audit Office and ARI both issued reports stating that the awarding of this concession to him had led to deterioration in the railway service. Montoto's partnership in this and other early ventures with Sergio Tasselli, a leading K-businessman, also raised questions at the time. was “quietly building an economic empire” that was growing “in the shadows,” and that his “associates generally do not come from the world of business but from the world of politics, such as former Montoneros leader Mario Montoto.” Instead of improving the train service provided by Metropolitano, Montoto reportedly directed Alejandra Rafuls to film train operations and to edit the film in such a way as to make it look as if customers were themselves responsible for the service problems. When Kirchner became president of Argentina, Montoto quit the presidency of Metropolitano and formed Codesur. and is said to be the main supplier of the Buenos Aires municipal police. Montoto has publicly praised Scioli as “a pioneer in the fight against insecurity” and lauded his “bravery and courage.” Montoto has been described as a creature of Carlos Menem who was later taken under the wing of Daniel Scioli. Another source, however, has stated that Montoto's relationship with Garre has not been as friendly as his relationships with former Defense Ministers
José Pampuro and
Arturo Puricelli, and that, by the same token, he is not as close to Cristina Fernandez de Kirchner as he was to Menem and Nestor Kirchner. Montoto has sold security cameras to Buenos Aires through the Global View company. Mototo's negotiations for security cameras with suburban mayors have been described as “rough” and as involving “allegations of overpricing.” According to La Verdad Online, “Many mayors complained about the pressures put upon them from above” to buy security cameras from Montoto, and despite the pressures, many of them “refused to work with Montoto.” ==Personal life==