That assembly hall is used only by the Mexico (now officially called Central America) Branch. JW's from the USA don't go there. There's a similar situation in the Rio Grande Valley, with 2 assembly halls almost literally across the border from each other (La Feria TX / Reynosa MX).
Assembly halls are big money makers for the WTS in Mexico. The current assembly hall rental fee (required 'donation') to use these paid-for facilities is 60 pesos per publisher, which is the equivalent of about USD$3.50. However, many Mexican families, especially among JW's, are poorer than their US counterparts.
When many JW families in Mexico are taking home about 150 pesos a day, a family with 3 kids as publishers are expected to pay up 300 pesos.
And for many assembly halls in Mexico, these are NOT suggested donations. Some circuits charge each congregation for their required donation, and in turn the elders charge each family for their part. I know of some congregations where the elders will go to your house and expect you to cough up your required donation before each assembly.
If you think the WTS grubs for money in the US, it's even worse in Mexico. Evidently, they weren't getting their expected profits in Juarez, so they'll just sell the building and pocket the profits.
In the end, this will be a better deal for the Juarez JW's. It will be a lot cheaper to pay a 'worldly' company to rent a building than to rent an assembly hall from the JW Corporation.