They are concerned about bed bug issue, etc. You can import as long as they're cleaned.
Note: the publications are available on CBSA websites, eg: www.cbsa-asfc.gc.ca/publications/dm-md/d9/d9-1-7-eng.pdf
Used or second-hand mattresses
You cannot import used or second-hand mattresses into Canada unless you have a certificate verifying that the mattresses have been cleaned and fumigated in the country of export. A letter, or any other document that clearly demonstrates that this requirement has been met, is acceptable if it is signed by a person qualified in cleaning and fumigation.
The key is to read the whole law. Yes, there are restrictions on the importation of mattresses and you generally need a certificate on cleaning and fumigation. HOWEVER, (and this is the key for your case): there are five exceptions under which you don't need to prove that a professional cleaned and fumigated the used mattress to import it (the law applies in all cases "other than" five exceptions). The second exception concerns Setter's Effects. Therefore, if the settler/immigrant has it on his B4 you can bring his comfy mattress in to Canada without needing to find an approved cleaner, getting a certificate, etc.
I read a paragraph explaining this on CBSA's website within the past year or so explicitly explaining in plain English that the restriction does not apply to settlers. I can't find that paragraph right now (they have so many pages that refer to immigrants and returning residents that I just can't find the right one) but law is very clear on this matter."USED OR SECOND-HAND MATTRESSES AND MATERIALS THEREFROM
This memorandum outlines and explains the provisions of tariff item No. 9897.00.00 in the List of Tariff Provisions set out in the schedule to the Customs Tariff which prohibits importation into Canada of used or second-hand mattresses and materials therefrom.
Tariff item No. 9897.00.00 reads:
Used or second-hand mattresses or materials therefrom, other than:
(a) mattresses imported under tariff item Nos. 9806.00.00, 9807.00.00, 9808.00.00, 9809.00.00 or 9810.00.00, or
(b) materials from used or second-hand mattresses, when imported after having been cleaned and fumigated, in accordance with regulations made by the Minister of National Revenue, accompanied by such certificates as are designated by the Minister of National Revenue;
Bolding and blue color on text is mine
. Note that the certificate of cleaning and registration is always required OTHER THAN when the mattress is imported as part of the following tariffs:
Tariff No. 9806.00.00 concerns bequests.Tariff No. 9807.00.00 concerns Settlers' Effects.
Tariff No. 9808.00.00 concerns diplomatic and consular personnel.
Tariff No. 9809.00.00 concerns the Governor General.
Tariff No. 9810.00.00 concerns military equipment.
In addition to all that, there is no exception for mattresses listed under http://www.cbsa-asfc.gc.ca/publications/dm-md/d2/d2-2-1-eng.pdf
(SETTLERS' EFFECTS – TARIFF ITEM NO. 9807.00.00) so they key is just to make sure your husband qualifies as a Settler (which if he's landing when he turns in his B4 and arriving in Canada with the "intention of establishing, for the first time, a residence for a period of not less than 12 months" shouldn't be an issue).
Hope this loooong post helps! This post would be much shorter if I could find that one paragraph ... however, this way you can have all the laws with you in case anyone questions you at the border