In that case they must be have been purchased by Mexican companies, whether outright or through some fancy deals. (Can be done in Mexico)
As far as I know Mexico has gone against the grain by actually opening up their market, not to be dependent on old and obsolete local and US rigs, barges and vessels.
Several Singapore companies has set up joint venture operations in Mexico to take advantage of the opportunities that is opening up there. They have moved different types of vessels and work barges there, but I don’t think they have changed flag. (Some may have put boats into joint ventures as their contribution though)
I loaded a Malaysian owned DLB on a Chinese heavylift vessel here in Singapore last year. They did ONE assignment in Mexico. (Setting a jacket, lifting the topside and run a short pipeline)
When the job was completed, which took 53 days, the barge was loaded back on the same HLV, which had been waiting in Mexico, and transported back to Singapore. I had the honour of offloading it as well.
Here is the DLB on the HLV:
This picture was taken on return. No change of flag, or senior crew as far as I know.
There are presently several Jackups being built for Mexican companies here in Singapore and in China. I have loaded one on a HLV this year and is now getting ready to load 2 rigs simultaneously on one Chinese HLV, probably towards the end of this month. That will be an interesting operation, although it is not the first such transport.
The same company has two more rigs nearing completion, but they will be carrier separately. (Probably to be loaded out early next year)