Rob,
It doesn't hurt to ask the dealer about the warr. If the dealer recommended that hoe, it doesn't mean he'll warranty it if your tractor breaks. My warranty specifies what is not covered and I quote "Utilization of non-Mahindra type front end loaders, mid mount mowers and/or backhoes may result in damage to your Mahindra Tractor and void this warranty. This warranty does not cover damage, as determined in the sole judgement of Mahindra, caused by non mahindra loaders, mid mount mowers, and/or backhoes". Mahindra buys loaders, mid mount mowers, and backhoes from various companies and authorizes their use on different model tractors. The warranty basically says that if Mahindra doesn't sell or authorize the use these mentioned attachments for your model tractor and you go aftermarket with one they did not sell as an option, it could void the warr. Read the fine print on yours. If the dealer tells you your backhoe won't void your warranty, get it in writing from him.
P.S. It's a great looking hoe. Maybe larger tractors don't require a subframe? Eventually I will get a BH for mine.
George