I'd always had this hunch! The bus recording was supposed to be 安全 but why did it sound like 安前.
Then I got affirmation from 《成都方言》
This, though, is the only evidence or documentation/reference I have come across talking about this phenomenon.
What other references or documentation exist talking about “前”与“全”不分 or 全 being pronounced qian in Southwestern Mandarin, or more specifically Sichuanese/Chengduese?