Hello Gehuleath77
As a general advice, if you allow, try to travel light-weight. Recently, I have seen tourists using XL and XXL bags, and I wonder why the bags get bigger and bigger. Instead, rather travel light-weight and use a washing facility somewhere while travelling. By doing so, you will do yourself a favour, too.
Using XL and XXL bags, you will not only face an issue on the replacement bus, you will face the same issue on the trains as well, which are not made to accommodate such large suitcases, especially during times with many travellers. Mid-sized bags easily fit between the seats, under the seats, above the seats, and in the baggage racks.
Kind regards,
Roland