Difference between 佈 and 布
This doesn't exactly match the usage you observed, but《现代汉语词典》 differentiates between 布 and 佈 as follows:


  布: 1. 用棉、麻等织成的，可以做衣服或其他物件的材料, 2. 古代的一种钱币, 3. 姓
  佈: 1. 宣告；宣布, 2. 散布；分布, 3. 布置


This would lead me to believe that the traditional character 布 is only acceptable in cloth-related compounds and that 佈 is correct in both 公佈 and 佈置 (and all related verbs). This doesn't account for the prevalence of 公布; perhaps that's a simplification that's been in use so long that it's now commonly accepted.

(Of course, as you said, in situations where simplified characters are used, the distinction is irrelevant.)