I'm not saying they hadn't been asked, but without granting permission
(which clearly they didn't, since the Scottish paper reported that just now Celtic had received that permission. Besides the fact that they pulled him from training is evidence enough Celtic didn't have the proper paperwork/legalities tied up) TFC obviously wouldn't be expecting their captain to show up at another clubs training facility.
Edit:
http://www.eveningtimes.co.uk/sport/...ddie-1.1077186
"The administrative issue which threatened to halt Dwayne De Rosario’s trial has now been amicably resolved."