The different fire warning apps used by neighbouring jurisdictions caused confusion during the height of the Black Summer bushfires, the royal commission has heard.
A fire spread map put out by ACT authorities also heightened confusion as it contradicted a map issued by NSW as the Orroral Valley fire was crossing into the state.
The Royal Commission into National Natural Disaster Management heard on Tuesday of the cross-border issues councils experienced during the 2019-20 bushfires.
Snowy Monaro Regional Council chief executive Peter Bascomb said while there was a "high level of co-operation" between the ACT and NSW fire services, a map put out by territorial officials when the fire was moving into NSW caused "a great deal of confusion" for residents.
"The [Rural Fire Service] made a prediction of the fire spread into NSW from the ACT and the ACT offered a different prediction which left our residents somewhat confused and ultimately the two jurisdictions worked together and issues a new prediction map, but nevertheless there was obviously some sort of failing there in that planning which wasn't the level of co-operation that I had been seeing previously in my time in the emergency ops centre," Mr Bascomb said.
The fire ultimately destroyed 10 homes in the Snowy Monaro area, Mr Bascomb said.
Snowy Valley Council chief executive Matthew Hyde said communications were so poor between NSW and Victorian officials during the fires "it was difficult to be able to tell what was happening".
When a fire crossed over into a different state, the jurisdiction where the fire began no longer updated it on their app.
"There were significant issues about the movement across the border and the maintenance of the app so that the community were aware of the oncoming threat of the fire," Mr Hyde said.
Mr Hyde also said a blue warning symbol sometimes appeared on the NSW Fires Near Me app when there was a fire burning in nearby Victoria, even if the fire had not actually crossed over into NSW.
"They were simply highlighting that there was the potential for fire. So it was unclear to the community [whether there was any danger]," Mr Hyde said.
Mr Bascomb said even the different colours used in the NSW and Victorian apps caused confusion.
"While the levels of warning are the same between the two states - Advice, Watch and Act and Emergency warning - only one of those shares the colour background, namely red," Mr Bascomb said.
"For NSW the background to the advice warning is blue, in Victoria it is yellow.
"So while the actual words are similar, if not identical, people looking at it just quickly and relying on the colour codes would be potentially misled by what is actually happening."
There was even mixed messages going out in the evacuation centres.
Mr Hyde said more than 1700 people in registered evacuation centres were told they could return to Tumbarumba, when in fact the road was still shut.
"They couldn't return to their community and then they had to return back to the evacuation centre," Mr Hyde said.
Most concerningly, Mr Bascomb told the commissioners a NSW official who came to help at the Delegate relief centre walked out once they realised it was full of Victorian residents.
"Our staff are clearly not trained to operate a relief centre and provide that level of support to the people that registered there," Mr Bascomb said.
"I therefore requested the NSW welfare agency to assist us in that process. They agreed and they did send somebody down. However, apparently I didn't make it clear in my request that it was Victorians in there, and it turns out that the person, once they arrived at Delegate indicated that they could not provide support to Victorian residents and turned around and left.
"That's a serious concern to me. It appeared based on that experience to be no particular arrangements for the support and movement of evacuees across the state borders."
Evacuees from Khancoban were also forced to go up to Wagga Wagga where an evacuation centre was stood up, even though it would have been closer to go to one in Victoria.
Residents were unable to return home for 12 days, which caused problems when they had stock to look after, Mr Hyde said.
The commission will hear from more councils on Wednesday, including Bega Valley and Shoalhaven.