AFP correspondents and other residents of the city described a tense 12-kilometre (7-mile) trip from Aleppo's battered east into government-held neighbourhoods, and back into rebel-held territory in Rashidin, west of the city.
After years of fighting and five months of siege, their final ordeal involved crossing three checkpoints, each more dangerous than the last.
The first was held by Syrian army soldiers, followed by a crossing manned by Russian officers and a third by Iranian and Iraqi fighters.
"Out of all of them, the Iranian and Iraqi checkpoint is the most dangerous," said one middle-aged passenger, who had been on a convoy that was turned back several days ago at the final crossing.
"God protect us from the Iraqis so they don't pull us off the bus and beat us like they did last time," he told fellow evacuees.
Thousands of people -- mostly women and children -- squeezed onto buses with whatever belongings they could carry, many in tears and others shivering in the cold.
Their gaunt faces and tattered clothes were covered in soot, after many spent the night huddled around bonfires to keep warm as they waited for the buses.
The evacuees pressed their cheeks against the cold windows to look at neighbourhoods they had not laid eyes on since 2012, when Aleppo was divided between government control in the west and rebels in the east.
- 'I'll come back' -
"God willing, I'll come back to Aleppo," one elderly man cried as he crossed through destroyed neighbourhoods.
Others took pictures with their cellphones, murmuring "We may never see our city again in our lifetime."
When they pulled up to the first checkpoint manned by a pair of Syrian army soldiers, the hum of chatter on the buses suddenly stopped, an AFP correspondent said.
Terrified evacuees tried to look at the fighters out of the corner of their eyes, and let out sighs of incredulous relief as they were waved through.
Next came a checkpoint with a group of blond soldiers from regime ally Russia, in flak jackets and holding bomb detectors.
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They stopped the bus for a nerve-wracking 30 minutes, pulling out suitcases and duffel bags to search them thoroughly.
"Does anyone want to get off and go to Hamdaniyah?" their translator called out in Arabic to the passengers, offering passage to regime-controlled areas in Aleppo province.
No one volunteered, and the bus lurched onwards to the dreaded last checkpoint of Iranian and Iraqi fighters.
Passengers waited with bated breath, peering out of the vehicle's windows at militiamen wearing patches from Harakat al-Nujaba, an Iraqi Shiite movement.
The fighters pulled out their phones and photographed the bus, laughing, before waving it through.
- Sleepless night -
Several thousand other evacuees, including Ahmad Raslan, were not so fortunate.
"We left on the buses at around 3 pm on Sunday and we were stuck until noon today. We were treated terribly -- they didn't even give us a cup of water," he told AFP.
Dozens of buses including his were detained for approximately 20 hours at the third checkpoint, and they were barred from getting off even to go to the toilet.
"The children were vomiting and the smell of the bus was disgusting," 23-year-old Raslan said.
AFP correspondents in the same convoy described passengers using plastic bags to relieve themselves and throwing them out of the windows.
Passengers stayed awake throughout the night, as the militiamen had ordered bus drivers to keep the overhead lights on inside.
Women read the Koran in an attempt to find solace, while men tried to keep children calm with a competition of who could stay quiet the longest.
On Monday morning, exhausted and traumatised, the evacuees were finally allowed through to rebel-controlled territory west of Aleppo.
When they reached the first opposition-held checkpoint, passengers hugged each other and burst into tears of relief.
Young men traded jokes while biting into bananas and sipping from bottles of water distributed by aid workers.
Others were more cautious, looking nervously at nearby rebels as if still in denial that they had finally crossed out of territory held by Syrian government soldiers.