If we assume that company question is about equities reported in S.02.01 in R0100 or holdings in related undertakings, including participations reported in S.02.01 in R0090, then:
1. We can confirm that Unit A (borrower) will present the loan as liability in S.02.01. Company shares will be reported as assets in S.02.01 and detailed information will be provided in S.06.02 (in this case in S.06.02 in C0100 option "1 - Assets in the balance sheet that are collateral pledged" should be chosen). Company shares have not to be reported as a collateral pledged in S.03.01 (this template is only for off-balance sheet collaterals).
2. Unit B (lender) will report in S.03.01 in R0100 collateral held for loans made or bonds purchased because it will be off-balance sheet item (company shares remain on Unit A balance sheet). In S.03.01 in C0020/R0100 will be the value of the company shares as of 31.12.20xx and in column C0030/R0100 will be the value of the loan provided to Unit A as of 31.12.20xx.

Additionally, this item will have to be reported in more detail in S.11.01 because this template contains an item-by-item list of off-balance sheet assets held as collateral for covering balance sheet assets held directly by the undertaking. In case of Unit B, in S.02.01 in R0230 will be presented loan as an asset, which in S.06.02 will be classified as "Loans made collateralized with securities" – CIC 82.

If we assume that company question was about own shares(held directly) reported in S.02.01 in R0390, then the concept described above is kept but in case of Unit A (point 1) own shares will not be presented in S.06.02.

Regarding examples for collaterals pledged which are off-balance, if for example an undertaking pledges as collateral an asset received through repo or security lending contract not recognised in the balance-sheet then this is a collateral pledged which is off-balance.