The lawnmower is mobile equipment as defined on the CGL form and the BAP, so any injury or damage that results from the use or ownership of the lawnmower will be covered by the CGL form. That also applies to the trailer while being used for the maintenance of the insured's grounds.

As for the 4-wheeler causing an injury or damage, the answer as to which policy applies depends.

If the 4-wheeler is subject to a compulsory or financial responsibility law or other motor vehicle insurance law in the state where it is licensed or principally garaged, the 4-wheeler is considered an auto under the terms of the current CGL form and the current BAP. In that case, the BAP would apply to a claim, and this would include the trailer while it is attached to the 4-wheeler. Of course, coverage under the BAP is for covered autos and the 4-wheeler and trailer have to have the proper covered auto designation symbol in order to be considered covered autos. Symbol 9, nonowned autos, is the designated symbol for those autos that the named insured does not own, lease, hire, rent or borrow that are used in connection with the named insured's business; this includes autos owned by employees while used in the business of the named insured.

Now, if the 4-wheeler is not subject to such laws, and it is designed for use principally off public roads or fits some other part of the definition of mobile equipment, then the CGL form would apply to a claim against the insured based on the use or ownership of the 4-wheeler.