I think both Post Canada and US Post Office either mis-understood the UN recommendations or took the easy way out and banned anything that required thinking.
It took a bit of searching but I finally found a copy of what I think was the origin of these rules: a UN document,
this copy, the DoD version, in pdf format is on the US Army site. If I read it correctly it says for ground transport the batteries must be packed according to the following rules. The first is for batteries containing sodium, the second lithium.
P408 Packing Instructions
* For cells, the certified outer packaging conforming to packing group II with sufficient cushioning material to prevent contact between cells, contact with the outer packaging, and movement within the packaging during transport
Batteries--
a. Will be protected from short circuit.
b. May be transported unpackaged or in protected enclosures (such as crates) that are not required to be U.N.-certified.
c. Will not be transported in a way that terminals are used to support the weight of other batteries or any other materials packaged with the batteries.
This only applies to UN 3292.
P903 Packing Instructions (note)
* Batteries will be protected from short circuit.
* Certified packaging conforming to packing group II will be used.
* When lithium cells or batteries are packed with equipment--
a. The cells or batteries will be packed in inner packing group II fiberboard packagings.
b. The equipment will be packed in strong outer packaging in such a manner that accidental operation is prevented during carriage.
NOTE: Only applies to UN 3090 and UN 3091.
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Limited info. was found on
this UN site