Prior to May 1, 2006 the mobile network operator LUXGSM used the numbering range 028 for its mobile voicemail service. Due to the common practice to omit the leading 0 when dialing a number from abroad, the numbering range 28 was aliased to 028 when called from abroad. This obviously rendered the numbering range 28 unusable for other services.
On November 1, 2006 all the numbers starting with 028 were finally disabled and so was the alias. Now came probably the more difficult part, most foreign operator charged calls to the numbering range 28 as mobile calls, but the range was now available for future usage as geographic fixed network numbers. Over 4,5 years later most network operators to be taken seriously should have updated their billing systems.
I haven’t seen any numbers starting with 28 in the wild, but EPT and VO already hold allocations from the 28 superblock.