I assume you are talking about the incident in 1995 where gunmen tried to assassinate Hosni Mubarak in Addis Ababa?

First off, the gunmen who fired at Mubarak's limousine were all Egyptians, and were members of al-Gama'at al-Islamiyaa ("Islamic Group"), an Egyptian militant Islamist movement with ties to al-Qaeda.

IG was tied to the 1981 assassination of Anwar Sadat because they were in coalition with Egyptian Islamic Jihad at the time. That assassination led to a government crackdown on the group. In 1991 membership had recovered enough to begin a violent campaign against the Egyptian government by murdering government officials, writers and literati, and foreign tourists. IG's purpose for this campaign was partly motivated by Egyptian government's adherence to the Camp David Accords and recognition of Israel. However, IG's larger goal was to topple the secular military regime which had been suppressing Islamist groups off-and-on since the era of Nasser; and to bring to power an Islamist government in Egypt.

---

With that information in mind, I'll address the government of Sudan's role in the assassination attempt.

In 1989 a military coup brought to power the al-Ingaz ("Salvation") revolutionary regime, headed by sheikh Hassan al-Turabi and backed by a coalition of conservative military officers, Islamist ideologues, and businessmen. Within this coalition, different elements had competing notions of how governance and foreign policy should proceed. Some Islamist revolutionary elements sought to spread Islamist revolution to neighbors in Egypt and Ethiopia. Business elements and certain military officers sought to moderate this revolutionary impulse and direct the regime towards national economic development.

Within the intelligence services, these differing ideologies played out in factional battles between officers of military intelligence, led by Muhammad al-Dabi and Elfatih Erwa; and their opponent Nafi al Nafie the head of external intelligence. Dabi and Erwa were career military officers who had enjoyed good relations with Eritrean and Tigrayan rebel movements in the 1980s during the Ethiopian civil war and sought to continue peaceful relations with TPLF-led regime in Ethiopia.

On the other hand, Nafie and other security hawks supported a policy of exporting Islamist revolution to Egypt supporting IG and Egyptian Islamic Jihad and in Ethiopia by supporting Muslim Oromo rebel groups. This faction under Nafie is believed to have known about and approved of IG's assassination attempt against Mubarak in Addis Ababa as a way of provoking a crisis and forcing the Ingaz regime to rally behind the policy of exporting revolution.

The location of this assassination attempt was also possibly an attempt to discredit Dabi and Erwa, because Elfatih Erwa was in Addis in the house of the head of the Ethiopian intelligence service at the time of the assassination attempt. The attempt infuriated his Ethiopian hosts who assumed his complicity in the attempt. On the other hand, the fact that an assassination attempt happened under his nose was perhaps meant to display Elfatih Erwa's cluelessness.

This answer is a close summary of Harry Verhoeven's explanation in Water, Civilization and Power in Sudan; the political economy of military-islamist state building on pages 118-120.